Think you'll get to the gym every day this week? Willing to put your money where your mouth—and butt—is? A team of Harvard behavioral economists created an iPhone app that lets you do just that. Every week, you can use the GymPact app to log your workout commitment: how many days you'll visit the gym (or yoga studio or tennis court or swimming pool) and how much you'll pay if you flake out. The theory: The only thing harder to resist than a "Mad Men" marathon or happy hour at T.G.I. Fridays is cold hard cash.
Users can check into one of the 40,000-plus fitness facilities in GymPact's database or add their own. GymPact uses GPS to verify facilities and will validate all but home and office gyms. According to GymPact's website, users fulfill their commitments or "Pacts" 90 percent of the time. When they don't, their credit cards are charged based on the individual stakes they made at the beginning of the week. (GymPact places a 30-minutes a day, 1-day-a-week and $5-a-workout minimum on Pacts.) Every Sunday, GymPact crunches the numbers. All the money collected from the people who skipped their workouts is divided among those who didn't. If you went to the gym all five of the days you committed, you'll get five shares of the total stake.
Play your gym membership cards right, and you could reimburse yourself for your next all-day lift ticket. Better yet, you'll be in good enough shape to enjoy it.