I started riding with a Garmin 500 to measure my cadence. Now that I know how a 90 PPM pace feels like, I've ditched the Garmin. Like others, I found the computer distracting and the heart rate monitoring useless. I do ride with an iPhone and spare battery in a jersey pocket or saddle bag. My favorite apps are Strava and Cyclemaster which I check out after my ride is over.