Fitsby is a mobile app that motivates you to go to the gym. You earn money for going to the gym, and it's paid for by people who didn't go.
Here's how it works:
1. You join a game with friends (or strangers) and compete on how many times you check in at the gym. Everyone places a wager and agrees to pay up if they are not one of the top three gym-goers of the game.
2. Check in at the gym using your smartphone's geolocation. You must workout for at least 45 minutes then check out.
3. At the end of the game, the top three gym-goers are rewarded money from those who didn't go to the gym as much as them.