For what it's worth, I use Cardio Trainer for tracking + social sharing. Friends "cheer" me on via Facebook, and I can progress my workouts using a myriad of tools they have. It's unclear what this does beyond that.<p>For what it's worth, if there were an app that helped me know WTF to do when it comes to building muscle tone/size, I'd happily pay for that. To an averagely fit guy (5.5 miles in 60 minutes or so, 2-3 times a week), the weights side of thing is infinitely more complex than the cardio side of things (which amounts to "keep your heart rate within this range for a long time").