So I was hoping to use some of the 41's collective knowledge to learn about options for using a smartphone as a cycle computer. Seems like a smartphone would have lots of features that would make it a great fit for a cycle computer, like a large screen, built in internet and GPS for maps, automatic synchronization of data with your other devices, etc. Basically you've already got lots of the ingredients to go up against a higher-end Garmin with a much lower cost. But using it as a cycle computer would probably require a good mount and dashboard-like software to use it effectively. What are good options in this regard? Are there mounts that provide significant weather protection? Also how do I get speed/cadence sensing?

Thanks for your input.

You'll also need to power it with a motorcycle battery if you want the screen on all the time.

I love using my phone kept in my pocket to record mileage, though

I feel better knowing that my cycling computer and phone are separate because you never know what is going to happen. I stash the iphone in a seat bag while the Garmin 500 tracks all important things. No need to worry about the phone dying, and in the unfortunate event of a crash, I know my phone isn't too vulnerable.

It is annoying to stop and access the wedge to find out where I am if lost, but its a small price to pay for a little sense of security.

I use an iphone 4s as my bike computer. I use this mount https://www.quadlockcase.com/ which requires its own proprietary case. Wahoo Fitness makes some cases/mounts which offer more weather protection.

For software, I recommend strava or wahoo fitness apps. Both support ant+ or bluetooth sensors. I am currently using the bluetooth heart rate sensor from Wahoo and it works great. Hope that helps.

It depends on how far and often you ride. I've always been using my iPhone as my GPS / biking computer using Strava and MapMyRide.
While iPhone is great to use and track your rides, the battery drains really fast - more than half after my regular rides, which are about 2 - 2.5 hours, and that is while running in the background.

That being said, if you plan on riding for short periods of time (under 3 hours), you might be fine with your iPhone as your cycle computer.

But, if you are planning to ride longer, or if you want to mount it on your bike to have it constantly on, you need something else.
Having it on all the time will probably drain your battery completely in under 2 hours. Plus, you don't want to drain your battery and be left without your phone while riding.

exactly!

I have tried using my phone but battery like was not very good on the phone battery alone, yes I have an external source also but not worth it and the phone does get hot.
I find it easier to just use my Garmin and forget about it.
I have used my phone on long trips with external power to transmit my location for family using programs like Glympse or Instant Mapper they can see data from computer or their phone on a map to track me live, phone is in saddle bag so I'm not using it for my feedback.

the GPS on my phone is horrible. It wouldnt be very accurate, but i guess it would be better than nothing. I wouldnt think it would give you much info w/o ANT+ adapter

- anything bigger than an iPhone (pre-5) screen, just too big. Super Freddy.
- screens aren't designed for constant sunlight view, you'll have to keep the brightness at max.
- not enough hardware buttons. you don't want to be swiping and pinching to zoom on the bike.
- add an external power source? ultra freddy.

I used the Wahoo Fitness case for a few months with an iPhone4. The case includes an ANT+ receiver so I added a speed/cadence sensor and a heart rate monitor. It all worked well and there are plenty of apps to collect the data. However, if you keep the screen on you can only get around 2 hours of battery life, maybe 3 at the most. Letting the screen turn off extends the battery life but what's the point if you can't see the data? As others have stated, it's hard to see the screen well in direct sunlight. In the end I switched over to a Garmin 500 and I could not be happier. Battery life is not an issue and the screen is very visible in all light conditions. If you do shorter rides the phone is an option, especially if you keep the screen off. But for longer rides and to see the data in front of you I'd spend the money and get a Garmin or equivalent.

You can do it but there are several drawbacks and tradeoffs:

1. Power drain - the GPS function is a major power drain on a smartphone and may make it a problem for longer rides
2. Display issues above
3. Durability - if your bike falls over (which happens!!) do you really want to trash your $300 smartphone??

That said, I do use the strava app on my iPhone. I don't have the phone "on" while riding though, I just push the "start" button, turn the phone off, and put in my jersey pocket.

I think that if you want a "real time" computer it's probably better just to get a dedicated device. Using the smartphone is a major compromise.