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.