Healthseeker from Ayogo through an article in Fast Company that Joe Pine, one of authors of Authenticity sent me. Enough links for you?
Healthseeker seems to be implemented very well. At the Game Horizon 2010 conference I talked about how games integrated with real life need to be:
4) Not embarrassing
Healthseeker seems to have numbers 1 and 4 down okay, but 2 and 3 are pretty tough. Healthseeker's focus on social networking is a good way to reduce cheating, but still, making something like this effortless is really hard. And then there is the shame problem -- once you make a few bad moves, it makes you want to avoid the system, which is easy to avoid, since you have to put in effort to interact with it.
Time will tell if this is the right approach -- Healthseeker definitely seems like one of the stronger health/diet apps out there! The Gamepocalypse will make you STRONG!