"Fitocracy turns fitness into a fun, addictive game to help motivate users to improve their fitness. You earn points, level up, and unlock achievements, all for tracking what youâ€™re already doing in the gym. As you level up in Fitocracy, you get harder challenges and need to lift more/do more challenging cardio to keep leveling. Throughout the game, users can complete special quests, unlock bonus features, and compete with their friends in order to get them to the next level. "
it's closed beta now, and is actually pretty fun and polished in my opinion.
i have 8 invites left, but can probably get more from the devs. if you would like to try it, SM me your email.