Here is a link to Marginal Revolution's markets in everything. The latest such market is StickK.com, launched by economists Ian Ayres and Dean Karlan, to facilitate personal commitment contracts to achieve a more healthier lifestyle.
If you want to quit smoking or reduce your weight and care ot able to do the same, no need to worry any longer. Enter into a contract with StickK, and pay some money upfront, with a contractual commitment to pay a fixed instalment to charity if you are unable to reduce and finally goive up your cigarettes or do fixed number of rounds or push-ups.
NYT has this article on commitment contracts to reduce weights.