I've been looking online and I've seen a few... Gym Buddy, iStayFit, Fit Phone, iFitness... not sure which is the best. My main concern is tracking/logging. I want to be able to log my exercises/reps/etc, and ideally be able to compare performance over time. Unless they have a good database of exercises, it'd be nice to be able to add custom workouts/exercises. Finally, if it happens to have useful demonstrations/instructions on exercises, that'd be nice. But I'd rather have great logging and no instructions than OK logging and instructions/vids.