In terms of the original question (ie: app to track indoor training) the best setup I've found so far is to use TrainerRoad with a speed/cadence sensor and use virtual power. It's just.. awesome, short of a real power meter.

But it doesn't seem to be Android compatible so if you just wish to track HR you have plenty of apps like Strava, RunKeeper, Endomodo etc. that run on Android. Tracking only HR is not really useful, but you'll get training times, and don't forget to add comments on how you felt the effort so you can correlate later on.