My game using Bullet has just been approved on the App Store. And I am very exited about it.
You basically shape your pet using blocks of various size. It then uses some Genetics Algorithms to compute a movement that will give it life and let it walk. During the learning phase Bullet is running in a background process and go through thousands of physical steps in just a few seconds - and this is on an iPad.
You will love to shape your pet with only a few leg and see him actually using it. Or give it a snake shape and see it crawl.
It's called Learning Pets and available for the iPad here: http://itunes.apple.com/gb/app/learning-pets/id530192045
Any feedback is very much appreciated.