The thing that's missing for me is suggestions on how much to lift / how many reps. There's a fitness program called 100 Pushups that came up with a good solution for that…
- Repeat the exercise (in this case, a push-up) as many times as possible until failure. A person might achieve 8, for example.
- The app comes up with a schedule; every other day, the user is expected to do a set of 3, 4, 3, 3, 5 (with a 2-minute rest between each set)
- The app's schedule has an algorithm that ramps up the reps at a pace that the user can manage — and self-adjusts if the schedule is too easy or too hard…
- until the user can do 100 push-ups at the 6-week period.
If there's any interest in this, I'd be open to discussing a UI and contributing.