I just recently have been trying apps as well. I installed Ride With GPS, Map My Ride, and Strava. I try them alternately and haven't really decided. I notice your past rides are only visible in Ride With GPS unless you're online. If you use Strava and ride a common bike route there will be some "segments" scattered along the way and the app will tell you if you've performed well against your earlier rides.

I think they all work with some external inputs like heart rate monitors. I don't know if they let you know the heart rate as you go. Just having it as a fait accompli record wouldn't be as valuable. Hope someone chimes in.