Very few people are any interested in a BT3 transmitter that 1) uses too many batteries, 2) is too big/bulky, or 3) requires recharging (given that it's likely going to be zip-tied to the bicycle).

Very few people are going to be interested in yet another box (they might have to spend $100 for) to deal with translating ANT+/BT4 to BT3.

It's unlikely that there's is any market for a box that converts analog wireless cadence/speed data to BT3.

If there was a large market for this sort of stuff, we'd already have seen multiple companies providing products!

You keep getting this backwards. The problem isn't the phone. It's the transmitter (which needs to be small and very low power).

BT3 has been out for a long while. If it didn't suck for this purpose, we would have already seen transmitters to support it!

you make assumptions that have no basis in reality.

Here is how "I" would build one of these if I had the means.

I would have a small black box that you would mount to the bike. this box would have space for 2 batteries roughly AA sized each. (this by the way is enough space for over 8 amps of cells in 18650 form factor)

you would mount this to your bike and affix it anyway you want. you WOULD NOT have to remove it to remove the batteries.

this box would have multiple connections onboard. you could then plug "SENSORS" into these ports.

say a cadence sensor and a speed sensor and a power sensor. do you need anymore? lets say we include 6 ports "just in case"

all of this would mount to your bike and be relatively permanent. no reason to move it around. THOUGH it might be nice to mount the black box in a custom "mount" so you could "wire up" multiple bikes and just move the "black box" from bike to bike. in fact that IS cool so that is the way I would go. figure this box to be able the size of a pack of playing cards. maybe a wee thicker 25% or so thicker.

now software on the phone would pair with the black box. the user would "define" sensor inputs. #1 is speed #2 is cadence etc.. etc..

I could even see wiring up universal power for ALL my lights (except the headlight it would use its own battery) to this same box and one of the "channels" would turn the lights on or off. you could even design the software to do this for you using the light sensor built into most phones or just press a button on the phone.

I could even see bikes coming "prewired" and you just plug in your black box and go. (I mean lets be real the sensors are just magnetic switches they are 10cents a pop in reality.

all the black box does is measure pulses from the sensors and send the PPM to the droid and its cpu does all the math to interpret that data.

It should be possible (in bulk mass produced) to make this for under $40. there really is simply NOTHING expensive going on here at all maybe even $20 from china. all the "hard work" is done by your phone. the black box just counts the pulses from the dumb sensors and sends the "rates" with an channel id to the phone over BT and we already know we can do a bt headset for $5 so that pat is CHEAP.

add a couple solar panels (would add a couple mm to the box thickness) and for the average casual cyclist I don't think they would EVER even need to remove the batteries to charge them up.

you make the silly claim that people don't want batteries yet they don't complain about having a battery pack they have to recharge DAILY for their headlight.?

I am a gadget guy. I want to "wire up" my bike. OK if your a racer you want sleek clean light minimalist. MOST of us are not under this category.

but we have to pay your "race guy" prices if we want this kind of fun stuff.

I think I KNOW why there is none of what I want on the market. I think its not cheap to "start up" production of a product unless you know you will sell MANY of them "OR" have a high enough "margin" to offset the startup costs.

so to offset the risk they go with tried and true. they target a market that is willing to pay premium prices for premium stuff. bt4 makes perfect sense for that market.

I have no doubt the prices will come down and in 5 years all our phones will be bt4 or some other new thing and these things will be cheap.

I am just annoyed that I might have to wait so long.

Yet another clunky box to strap to your bike. Yuck!

A wireless computer with wires?? Yuck!

Six wires? Yuck!

With 2 or 6 wires, it's certain that people are not going to want to move it!

Yuck! Yuck! Yuck!

More freaking wires? What phone has a "light sensor"? Bizarre.

More wires? And you want something cheap???

You are pulling guesses out of your nether regions.

Right now, you can buy a BT4 speed/cadence sensor for $60. It's a real product. And it's not the complicated, ugly mess you are proposing!

The lights aren't zipped-tied to the bike. If people could get sufficient light output without recharging, they would certainly choose that!

There's no reason to have to recharge a speed/cadence sensor after five hours!


All this to avoid spending $60 (and having a new phone)??

well at least you added the and having a new phone but failed to mention the $500 or more price tag for that new phone.

your starting to come around. lets keep at it.

"Yet another clunky box to strap to your bike. Yuck!"

why do you CARE? of if your a racer with a nice high end bike and a higher end income to support that higher end bike OK I can understand. GREAT go buy your $500 phone and your $80 a month plan to go with that phone if you want.

"A wireless computer with wires?? Yuck!"

there is no real reason EXCEPT for aesthetics to NOT have "wires" on the bike. your never going to move them EVERY again so what difference does it make. you already have a CHAIN running all over the place and 4 CABLES running all over the bike. so what if a couple wires are on the bottom of a tube that the average person won't even notice.

Lower maintenance and no batteries (in sensors) to change and now the sensors are pennies a pop instead of $20 $30 $40 a pop.

the WIRELESS is simply to get the info to your PHONE. the idea is to avoid needing that $200 $500 $800 garmin computer.

"Six wires? Yuck!
With 2 or 6 wires, it's certain that people are not going to want to move it!"

more ports means more functions. for us tech geeks thats more fun.
what is with you and this disgust over wires? why do you care?

I ride a day 6 dream 21. its a gigantic 40 pound semi recumbent. I am going to have bags and racks on this thing. lights all over the place (I plan to light it up like a christmas tree) and even a trailer on the back (working on that)

do you really think I give a monkey butt if it has a few extra wires or a deck of cards sized little thing hanging on it somewhere?

I am a 6'4" 455 pound monster. thats not even as big as my "HAND". just one hand.

what makes you think I would give a crap about those wires and box ?

"More freaking wires? What phone has a "light sensor"? Bizarre."

MOST droids have a ambient light sensor to auto adjust the display brightness based on the ambient light level.

dimmer inside brighter outside daylight etc.. etc.. this is a standard feature all but the "cheapest" droids have it to the best of my knowledge. in fact of all my phones and I have some cheapies only the prevail lacks a ambient light sensor.

"More wires? And you want something cheap???"

you do realizes wires are cheap right? pennies? I can goto the dollars store and with $1.06 get enough wire to wire up 30 bikes.

its the independent transmitting calculating sensors that cost a lot of money. wires eliminates that. makes it CHEAP.

"You are pulling guesses out of your nether regions.

Right now, you can buy a BT4 speed/cadence sensor for $60. It's a real product. And it's not the complicated, ugly mess you are proposing!"

guesses? sure but VERY educated guesses. I actually think this could be chinese built for $10 to $15 if the software task was taken up by the open source community.

I said $40 to be VERY conservative.

as for $60? I can show you a cadences speed sensor in bt4 for $40.

but its a paperweight if you don't have a bt4 device and "as of right now" its very EXPENSIVE to have a bt4 device.

for the "average person" to get a BT4 device would require a $200-$300 phone (thats WITH CONTRACT) at minimum $80 a month.

for me that is $250 (for the phone I want) plus an extra $24 a month (and only because I have access to an account structure that NONE OF YOU CAN have access too)

this kind of upgrade is "permanent" so thats around another $2500.

now if you already HAVE this kind of phone and service GREAT but if you don't your talking about a potential $3000 or more in "costs" just to get bt4? or wait a couple years for cheaper phones to come out.

you could just buy the phone outright used without service but now your looking at $500 $400 if your lucky.

might as well buy the garmin at that point.

and where do you keep getting this 5 hours CRAP from. why do you keep pulling that clean out of your butt?

with the 8amp pack I suggested (wee larger than 2 AA batteries) you could run MONTHS AND MONTHS between charges. probably have to charge ONCE at the start of each season.

I suspect that ("soon") every new phone, regardless of price, is going to support BT4. There's no reason not to (if they support BT at all).

From you (of course).

2 AA batteries is too large. Way, way too large. You can get months out of a single coin battery.

Even better (that makes my argument stronger)! Show me!

Show me!

It's dopey to go through the effort of adding wires to a wireless system (especially, when it's easy to avoid the wires).

You are one person. You don't make a market.

So what? They are unnecessary.

$40 eliminates all those silly wires and the big-assed block.



Why would the "open source community" be interested in this crappy market?

Do you really think that it's going to take less time to have the "open source community" and the "Chinese" to get a product into your hands?

You can buy a phone outright for $600.

Go for it! (But it's going to be hard to make calls on the Garmin!)

you presume I have the MONEY for a garmin. I do not that is why I looked for a DROID solution but the only current droid solutions require me to spend MORE MONEY than the garmin costs. Grrrrr :-)

I hope your right (about all new phones having bt4) but I don't think so. they don't even have all the API's finalized for bt5 on android yet.

I estimate 2 years before deep penetration of bt4 as in "its in the cheap phones"

I don't have any idea what you have the money for.

I do know you don't "need" cadence data to be sent to your phone (it's just a "nice to have" thing).

Looking at the sorts of cycle computers that have been available for quite a number of years already, it seems that people want smaller and less wires (less complicated). If that is the case, then it seems unlikely that somebody would expect to make money making a bulky, wired intermediate, complicated device.

ANT+/BT4 transmitters are cheap and simple and are available right now.

Given how long BT3 has been out, if it made sense to have a transmitter that used it, you would be able to buy one. That you can't might mean that it doesn't make engineering/business sense to do so.

Typically, technology companies target "wealthy" markets and let the technology mature (get cheaper) to target "less wealthy" markets. At this point, it doesn't seem to make much sense to invest engineering to target the BT3 market when BT4 is substantially better.

Yup. It could be 2 years but your alternative isn't going to be available any sooner (it won't ever be available). The "cheap phones" probably won't be able to do what you want anyway.

"ANT+/BT4 transmitters are cheap and simple and are available right now."

except Transmitters are useless without a reciever.

and even the CHEAPEST droid phone can handle "ANY" cycling demands without even breaking a sweat from a horsepower perspective. think about if you can buy cycle computers for $4 how much horsepower do you think those things have? all their doing is counting pulses. literally. thats it.

the slowest droid I am aware of is 600mhz. how fast is that $4 cycle computer? 4mhz ? if that? all it has to do is "count" and reference a table of values.

I doubt it will go anywhere but I am going to look into a homebrew option just to see how feasible it is. I can't do software but I can do "some" hardware see if I can find anyone to help.

do I need cadence and stuff like that?

careful there buddy need is a powerful word. the only thing I "NEED" is food, water, air and some shelter depending on what region of the planet I am in.

by definition ANYTHING else is a "want"

I WANT to be able to do this stuff.

what irks me (again) is that I have this insanely powerful computer and a $10 adapter that no one has made is the only think stopping me from doing some neat things with it.

trust me $40 for that cadence sensor is massively over priced versus "unit cost" but most likely that company has a lot of "up front start up" costs to offset so its understandable.

Regular BT is already "cheap and mature"

like I said. because of how cheap it is I am surprised no one has made anything. not even the chinese makers. just seems "odd"

There is no question its possible and feasible. I don't mean to insult but thats not even up for discussion I know enough about the tech and how to do it to KNOW its very feasible and possible.

I can only think of 2 reasons no ones done it.

no one thought of it (smart phones of this caliber ARE really very new still)

or more likely. the market really is just that small that they must shoot for the "high end" first to make a real profit.

We've gone over that.

No one is going to buy the device you are describing.

We've been over that too. Too power hungry.

We've been over that. It's too power hungry. No one would buy the device you are talking about.

Yes, it's "feasible and possible" but that doesn't mean anybody (enough people) are going to buy it.

No one is going to buy a overly-large wireless transmitter with a mess of wires.

The second one is a good guess (I mentioned it earlier)!

A third reason is that BT3 would require too large a transmitter (no one would buy extra overly-large box).

"We've gone over that.

No one is going to buy the device you are describing."

We've gone of this. your not in a position to make that declaration with anything more than your say so out your butt.

"We've been over that too. Too power hungry."

We've been over this too and your nuts. its not even close to be "too power hungry"

"We've been over that. It's too power hungry. No one would buy the device you are talking about."

We've been over this too. twice in the same post actually. your starting to get repetitious on me. you ok?

"Yes, it's "feasible and possible" but that doesn't mean anybody (enough people) are going to buy it.
No one is going to buy a overly-large wireless transmitter with a mess of wires."

Your not in a position to make that judgement. and you have "zero" data to back it up.

size is irrelevant. the only people who care about size are people (apparently) like you who likely have very expensive sleek bikes and expensive hardware.

the "average" person really does not "care" whether it has wires or if its just small instead of "tiny"

you keep saying my downright TINY concept is "overly large" and your being dishonest to use those words. what I describe is SMALL. what you want is not small. what you want is TINY. teeny tiny.

there is a difference.

"A third reason is that BT3 would require too large a transmitter (no one would buy extra overly-large box). "

we've gone over this. you have no position to make this declaration. and you keep using the wrong words.

you try to "wiggle" word out by adding "overly" to qualify large but your still using the word large and that is intentionally dishonest when describing something that is downright small.

Strava, fun and challenging.

I got some feelers out regarding a BT based cycling computer. no road bikers are not going to be into that but us "tech folks" don't care about that kind of stuff so we are fine sticking a tiny little box and some wires on the bike.

who knows if it will go anywhere.

on the other hand I got my S3. for FREE. man I love free.

I upgraded my account and got an Iphone 5 for $215

right their at the counter (I never even HELD the I5 still in the box) I handed it to my victum errr I mean customer and he gave me the S3 I want (BLUE too !!) and $225 in cash.

so not only did I get it for free but I made $9 on the deal more than covers the gas to meet him at the mall :-)

I have 2 more accounts I am going to try and do the same thing with both of them.

why? why not. it won't cost me a dime and S3's would be good "trade stock" for up-trading on craigslist :-)

I5's might be better trade stock but I don't like I5's and incase I decide to keep one or both I want to be able to use them so will go the S3 route.

so why would this guy give me his $400 S3 and $225 in cash?

#1 he needed an I5 (work)
Resale value on the S3 is $300 quick $400 if you wait a bit.
add the $225 and he has a potential $625

current grey market value of an I5 starts at $750-$850 around here and I can offer them BNIB.

its weird but it works out for both of us equitably.

but I have to do this within the month.

once apple catches up on stock the grey market value of the I5 will go down closer to "retail" value and trades where I spend NOTHING (in the end) will become harder to impossible :-)

I like endomondo, it's free and I use it for running , hiking and biking. Let's me keep track of everything in one place.

One that overwhelms, and blocks all the phones of people driving and BSing at the same time would be good.

actually yuo "can" do this but I would not advise it. for around $100 you can get a couple of battery powered jammers that have a pretty decent range. you need at least 2 jammers. a 3 band CDMA jammer and a 2 band GSM jammer.

BUT the range is short enough that they will be dangerously close to YOU when they totally stop paying attention to the road and start paying sole attention to their phone trying to figure out why its not working.

ie "NOT GOOD" :-) hehe

I used to have a radar emitter unit in my car. hit the button and watch all the "brake lights" turn on as people's radar detectors went nuts :-)

I tried them all - all had one major issue. If you are riding over 4 hours not only does the phone go flat (constant GPS) and render your progress 'unfinished', your phone is dead and now you have a problem if an emergency arises as you cant call anybody.

I 'saved my pennies' for a Garmin 705 - 12 hours of constant battery, waterproof and rock-solid reliabiltiy. Best piece of kit for a longterm rider.

Keep it simple and ride more.

yeah unless you have a higher end phone or an extended battery or an external battery 3-6 hours is about the limit.

my phone I run strava and icardio plus BT to the HRM plus BT to a speaker unit and run my music/podcasts in the background and keep the screen on. 1 hour takes about 15% of the battery so I could safely go around 6 hours to 10% charge left.

turn the screen off and I can add 50% to that. but thats a pretty nice phone with an optimized rom.

the advantage of the phone is not battery life. most people would need to add a battery pack. the advantage is the battery pack to get 10-15 hours run time on your phone costs $30 while the garmin "starts" at $250+

$500 if you want a nice unit. (the $250 garmin is not so hot) $800 for the top end unit.

now if you ride hard core and have the discretionary funds to buy the $500 or $800 garming. absolutely. go that route.

many of us don't have that much cash :-) smartphones are relatively cheap. extended batteries are dirt cheap.

even if you don't have a smart phone you can buy a samsung vitality for $40-$60 then add an $8 extended battery and your now good for 8-12 hours of run time depending on if the screen is on or off.

add another $30-$40 for an HRM ($80 new) and your doing everything the garmin does (almost) for a fraction of the price.

its all about compromise. the garmins are GORGEOUS units. but you will pay dearly for that gorgeousness :-)

I too was running a custom ROM on Android but I really need my phone for emergency situations. I bought one of those Duracell extended batteries but it was just another item to charge and remember - it became a pain. Eventually, I paid $290 for my 705 on eBay two years ago and it came with the HRM and Cadence (refurb). I live in WA so the unit MUST be waterproof. My phone was not usable as it rains 50% of my rides. Putting it in a case had its issues too (non-responsive to touch etc). In the end I was so frustrated I spent the $.

Yes you can buy a cheap phone (Samsung Vitality) but then your hooked into a monthly cell phone service just to use the phone on Strava etc. Its a paperweight without service. The garmin needs nothing but the outside air to operate. It comes with a mount and everything to get you going. Its designed to do the task and fits in minutes. No need for extra batteries, cables, special mounts, waterproof case, etc. It just works and works very well.

IMHO - spend the $300 and get the tool specifically designed for the task. Ive completed 100 mile centuries with my garmin (10 hours) and its as easy as an on/off to track EVERYTHING from the ride including feet climbed/heart/distance etc. Post-ride you plug the unit into your PC and all your ride data is saved to the Garmin website (or other of your choice) and all your stats are there instantly. I have over 4000 trouble free miles on the unit.

https://www.ebay.com/itm/GARMIN-EDGE-...item519f103d41


If mine broke tomorrow Id sell stuff to buy another - their that good.

wow $290 WITH the HRM/Cadence is a pretty sweet deal for a 705. I might even be tempted by that if I had the cash.

as for the vitality I want to touch on that again because you expressed the same misconception that a lot of people express. The monthly cell phone service.

ahh what monthly cell phone service? I have 4 vitalities 3 scores an evo and a prevail (busted) NONE of them have "cell service"

(side note WHY do I have so many? I got 6 scores for $30 a pop and 2 vitalitiy BT speaker combo's for $50 a pop. I sold 3 of the scores rooted and cracked for enough cash to pay for the other 3 scores both vitalities and to let me buy 2 more vitalities without speaker used (better camera) so they cost me nothing. literally :-) (cricket had some crazy deal going with best buy the bt speakers alone are worth $180 a pop and worth every penny (insanely good sound) so yeah I mean it when I said crazy deals.

I use them as "timelapse" camera's (I am big into photography) anyway onward....

these are not phones in the true sense of the word. they are quite literally little and very powerful hand held computers. that just happen to have a "phone" built in. not unlike your computer having a "modem" built in.

disconnect the modem and UNLIKE phones of past this handheld computer functions just fine. you just don't get live data from the internet.

and you don't need it either. I let my sisters bfriend carry one of my scores with him running strava. he hits record and just stuff it in his bag or his jersey pocket and "forgets about it" when he is done the ride he hits done.

when he gets home and wifi is available the phone simply syncs with strava at that time.

even on the stock battery that little zte score will go 6-7 hours maybe longer. gps does not take all that much power its the SCREEN that slurps the amps out of those batteries the screen and the radio's. screen off and radio's off and no slurping. phone will go WEEKS between charges.

when he did the MS150 I wrapped the usb cord around both the phone (defy xt in this case) and the battery pack. plug it in and hit go he stuck it in his jersey and never touched it.

strava recorded his ride and family gps tracker let us keep live tabs on where he was on the route.

that $28 battery ran the phone for over 10 hours of actual on time live tracking and strava recording AND only used about 40% of the battery packs capacity AND left the phone with a 100% charge.

the battery is a 5000mah VAAS pack. its about the size of a small wallet. just a little bigger than a 3.5" smart phone.

oh and the defy is waterproof. if you want a nice cheap waterproof droid get a boost mobile HYDRO.

$129 and waterproof. you do NOT need service to use the phone. service is only for making calls or sending data wirelessly over the cell network. the phone works fine and wifi works fine without a cell plan.

plus. me and rain don't mix. rain means I stop riding. immediately :-) rain is a really quick path to crotch rot for me and no riding for a week while it heals. :-)

garmin better? absolutely. but if you already have a viable cell it gives you FREE options to do the same thing the garmin does.

Well not really, your comparing apples to oranges. I thought you were using the devices as a garmin is used - with screen on during the ride so you can actually monitor your stats. A 'gps only' device would not work for me as I want to monitor my cadence and hear rate as I ride - isnt that the point? Youd be amazed how much further you can ride if you can watch your heartrate climb on the screen and know your working too hard and pull it back a little. I rode 200 miles in 2 days using this approach at 300lbs. And then there's cadence - whats the point in only knowing your cadence when your home? The point is to adjust your pedal stroke as your riding. Also, have you ever been riding on a long stretch of road and cant figure out why your tiring? The garmin shows you the % grade of hill in real-time. Youd be surprised how many times your climbing and not aware of it.

Again, to each his own, but for $300 to have the ability to monitor my speed, climb, heart, cadence, dist, avgs etc as I ride is well worth it.

nope comparison was apples to apples.

a $20 cycling computer will do everything your garmin does minus the gps for the most part. (for real time while your riding data) it just does not "RECORD" anything.

the point of the garmin is to do what the DROID also does. to RECORD the data and attach it to GPS data.

he had a cycling computer giving him his heartrate cadence and speed.

the droid was a cheap way to "log" the gps data for later review.

with a little cash the droid can "do" what the garming does as well. both displaying and recording and integrating the data.

there is no question the garmin is the superior tool. but it comes at a price. if you LACK a droid etc.. and want what the garmin can do.

then the garming is cheaper if you can find a refurd like you did or a cheaper model.

but if you HAVE a droid (they activate a million of them a day now) and you don't need 100% of what the garmin does AND you don't ride 10 hours a day.

then the droid can give you 90% of what the garming gives you at little to zero cost.

thats all. no big deal.

I agree that a $20 cheapo comp will do speed/dist etc but it wont do wireless heart and cadence.Those run closer to $100 and above. Neither will a Droid without expensive add-ons. If at all. Id say the Android software route is fine for casual hour rides around the park etc but as fitness levels evolve and you are riding further and further a need for the whole package will arise.

I went the route of the cheap comp(s), android software, extender batteries, cables and those experiments cost me around $100. They are all now gathering dust. I wish Id have gone the 705 route from day one and saved myself the $100 - but tinkering is always fun. Part of the process.

sorry dude, you don't get to add quid pro quo's to the equation. wireless is your problem ie thats a luxury. fact is a ~$20 unit WILL give you cadence (there is a 7 in 1 or 9 in 1 on ebay for $22 shipped does speed distance cadence temperature averages etc.. pretty nice unit too and a big screen thinking about getting one for just that reason. ie I can turn off the screen on the phone (it can get bright at night)

heart you do on a separate device. I have a watch that cost me $7 shipped ($6.83 actually). every now and then I touch the sensor and it tells me what my HR is. (before I got the BT unit)

so "real time" data is never an excuse.

the ONLY reason to get a Garmin is to do what "high end" droids do. real time data and RECORDING and Integration with GPS track information.

otherwise you only need $25-$30 in stuff to give you everything the Garmin does minus the logging and gps.

again. a new user to cycling who is casual (ie 90% of the cyclists out their) are NOT going to plunk down $500 for a Garmin (or spend time hunting a used one for $300)

there just not.

but if they already have a droid they can do ALMOST all of what the garmin does for FREE. the ONLY thing extra you get from the garmin is HRM and Cadence. (feature wise)

for $7 they can get a HRM Watch and for $20 they can get a cycling computer that does cadence. for $30 used (your using used garming prices I can used used prices too) they can get a BT HRM that will auto log the data with their droid just like the garmin does. for another $40 they can add a wireless cadence sensor IF they have a BTLE compatible device.

not saying it better (though it is better for me and my conditons) but its possible and its MUCH cheaper under the right conditions than the garmin.

BTW as proof. you can get a Cateye for $37.99 shipped on ebay

non name brand you have this one for $20 flat shipped
140825423299
and this one for $17.99 shipped
290761341048

so yes for just under $25 minus gps and logging I can do everything the garmin does and give me live data on the bike. ($17.99 cycle computer with cadence and $7 HRM Watch)

again the garmin is gorgeous (edge 500 kits $286 on ebay BTW) but its also extremely expensive.

BTW for those who don't have the cash for a garmin and do not have a DROID and can live without gps logging

$99.99

370663375058

and all wireless and watertight.

Then neither do you

The wristwatch HRM are garbage under $100 - Ive had two of them and threw them out as the readings were all over the place. You cant compare them to the garmin HRM chest strap - they dont work the same way. The garmin is quality kit. Ive also tried the cheapo cadence meters. It lasted three weeks before falling apart.

Just because an item is $20 and claims to perform a certain function doesnt mean that it can for the long term or at all. I have a chinese eBay 'wireless' cadence comp that used to claim my average cadence was 600rpm - thats some performance when the average is 85rpm !

If we are dumbing down to the cheapest items without taking into account accuracy and build quality then I can go one better than your eBay items. How about pen, paper and a map. Take your pulse by hand, navigate by the map and calc on paper your speed using your time/distance with pen and paper