Tapbots has released their first iPhone app to the App Store last week. Weightbot [App Store] is a weight tracking program for the iPhone, but appears to be particularly well designed.
Weightbot is a weight-tracking robot that helps you lose weight. Whether you are trying to lose (or gain) a few pounds, tracking your weight has never been more fun. Set your goal weight, record your weight at any interval (one weight per day max), view your BMI, and see your progress on a beautiful graph. Weightbot also has a built-in secure password feature to protect your weight from prying eyes.
The developer video captures the streamlined user interface:
App Store Link: Weightbot