In an attempt to gamify my own fitness, I wrote a simple workout tracking app that used energy bars which depleted and refilled over time. If I hit a particular muscle group that day, the energy bar for that muscle group would deplete and take a couple of days to recharge. The idea was to keep all the muscle groups on cool-down. It was actually quite fun for a while. Kind of like looking at a simulated representation of your body recovering over time.
