FYI, seems like there is an upcoming product called Pedal Brain that will plug into the iPhone/iPod touch and allow it to receive signals from an ANT+ sensor.

Here is the link for the TechCrunch story and the link for the product.

Also, I don't have any affiliation with the company. I just thought this might be of interest to some people.

Shows promise, but battery life may be it's demise.

They should sell a version with an external battery pack to boost the lousy battery that comes with the iPhone.
Apple should also sell an iPod with a built-in GPS so people don't have to buy the iPhone and lousy AT&T service.

There are multiple dynohub-type chargers on the horizon.

The company has a twitter stream, and they (he?) claim that they're going to get battery life up to 8 hours. I agree that an external battery (or allowance for same) would be a good idea.

I absolutely hate having to pay monthly fees for 'subscription plans' to be able to use software! If they go this route, they won't get my business-period! The fees associated with the iPhone itself are bad enough-I don't want or need any more monthly drain on my budget.

Having said that, I do like the idea and have been waiting for someone to come up with this solution (ANT+ compatibility for the iPhone).

Seems that this would be even more expensive than a GPS unit (the Garmin Dakota 20 is ANT+ compatible and costs $350). (Note that the Dakota 20 can't measure speed based on wheel-rotation because there is no way, as far as I know, of inputting the wheel size.)

big time PLUS one

Bad iDea: iPhone is fragile and not weatherproof. By the time you add all the accessories to make it work you will add weight and spend enough money to get a real high-end computer or GPS receiver.

Adam

Yeah, the real issue is the cost over and above the iPhone. With Garmin Forerunners and Edge 305's coming down in price, they've become cheaper than the iPhone's accessories. And the iPhone is about $60-$80 a month right now. Just not cost effective. Garmin could jump the iPhone pretty easy by adding a Wi-Fi connection to upload the files to the web.

The "$60-$80 a month" cost for the iPhone isn't relevent because the only people who would reasonably buy the pedalbrain stuff already have the iPhone (and are spending the "$60-$80 a month" regardless).

I'd guess there are better features than Wi-Fi for this very-limited purpose to add to a GPS.

+1 Doesn't seem liike a good idea to me. GPS devices are getting cheaper and cheaper. IPhones are expensive, fragile, poor battery life, ...

Also people keep forgetting that iPhone uses assisted GPS: GPS signal plus cellular tower triangulation. The GPS antenna is weak and without cellular signal assistance it becomes pretty useless as a GPS device. Plus its compass is ridiculously sensitive to electromagnetic interference. Save your money towards are real GPS receiver.

Adam

I don't dispute that it uses assisted GPS, but what is your basis for saying that it's "pretty useless" without the cellular assist? I haven't had trouble getting a lock on my iPhone when I'm outside of cellular coverage. Admittedly, it's the only GPS device I've spent any time with and I haven't done a rigorous study of how fast it acquires a lock. But it does work.

On my iPhone without cellular coverage the accuracy is several hundred feet which is useless. My Garmin GPS can do something like 10 feet.

Adam

i love my 705. i somehow feel that it live in the back of my closet 2 years from now and feel like a relative of the ancient 205 that moved in this space first.

I'm not sure about rain-resistance, but for sure the screen requires human finger touch to activate the various soft buttons. It won't respond with a gloved hand. Riding on a brisk day you need to remove your glove to use the screen.

Does the software cancel the screen-saver timeout? If it does you wouldn't need to use the touch-screen quite so much.

I hope you don't mind if I fling a pile of techy questions at you. Just tell me if I'm barking up the wrong tree.

Is the tower info just there to handle satellite shadowing and the resulting "urban canyons" issue? Or is it necessary under open access conditions?

Is the inertial navigation system (INS, for a compass and a multi-axis accelerometer) based on a MEMS chip? or what? Some automotive INS developments are finding COTS MEMS to be inadequate. Path prediction software based on INS and GPS makes it a lot more accurate and robust.

How does the EMI sensitivity manifest itself?

Some of this sounds like design issues rather than basic technology inadequacy. Hopefully Apple will do more product improvement (AND ATT will cut the price!).

The other Adam probably knows more about this stuff than I do. Tower triangulation gives the iPhone a location lock much faster, and obviously works indoors. But I don't think it's necessary.

AFAICT, there are some GPS apps that use accelerometer inputs as a cross-check on the location inputs (I know Motion-X GPS offers this as an option), but I don't think any of them really require it. OTOH, I've read of a non-nav app that uses the accelerometer only for measuring a car's performance, and it's been found to be as accurate as fairly expensive single-purpose testing equipment. Although I imagine there would be more "noise" when using an accelerometer on a bike that would confound that use. I do believe the iPhone's accelerometer is a MEMS chip.

I have the iPhone 3G, so I have no idea how well the compass works. Nav apps can and do work out your heading based on a series of trackpoints even without a magnetometer.

One Achilles' heel for all bike-computer apps is altitude. From what I understand, Garmin's own devices don't do a great job on altitude, and use desktop software to apply after-the-fact corrections. I know of one iPhone app, GPSies, that does after-the-fact altitude correction via the GPSies website; I'm not clear on this, but I think there are a couple others that will do on-the-fly correction internally by referencing online sources.

I've recorded tracks using a couple of iPhone apps and am going to try a third today. So far they've overlaid very closely over the road maps (though I noticed one spot on a bend where I seemed to be riding through a field). My guess is that I'm within 10' 95% of the time. I have not tried this with the phone function turned off, so I can't say how accurately they'd perform in the absence of tower data.

GPS is inherently poor for altitude determination (It's designed to locate a spot on a idealized two-dimensional surface). GPS devices that do altitude "well" use a barometer.

My Garmin Edge 305 has a barometric altimeter. The barometer is assisted by the GPS, so you don't have to calibrate it every day like most barometric altimeters. It works pretty well.

Note that cyclists tend not to care how high they are. They care mostly about cumulative attained altitude. Barometers don't need to be calibrated to absolute altitude for the latter!

True. I just care how high my riding partners are.

I've been experimenting with different iPhone apps on the bike and have written up some observations. Not the Pedal Brain yet, so don't get too excited.