iOS/Android: Pact, formerly GymPact, pays you money for exercising (and charges you when you don't). Now, it can help you eat better as well. Pact now tracks food and nutrition, syncs with MyFitnessPal, and has photo verification to prove that you're actually doing what you promised.
The service has changed its name to Pact (existing users will see the new name and features when they update the app), because it tracks more than just your gym-going habits. Just like before, the app asks you to put your money where your mouth is and commit to regular exercise. Go to the gym and you get cash payouts -- both from your own money, and the money of people who didn't go to the gym when they said they would. Miss the gym, and your money goes to the people who went. Now, the service is expanding into food and nutrition as well.
Here's how it works: Commit to a certain dietary goal, like eating veggies with every meal, or cutting out carbs, or just remembering to log your food. Put up a little bit of money to make sure you actually do it, and every time you do what you've promised, take a snapshot with your photo and upload it to Pact. At the end of the week, if you've hit your goal, you'll get to keep your money, and you'll get money from those people who missed their goal (about 30-50 cents per activity, which can add up if you're doing something daily).
Gympact doesn't deal in a lot of money -- it's just designed to offer a little financial incentive to get off the couch or eat smarter. The service even now syncs with MyFitnessPal, so users there can trade data back and forth to make sure Pact is properly updated. Hit the link below to read more or give it a try. The apps themselves are free at Google Play or in the iTunes App Store.