I started working on this project a couple of weeks ago. I was looking for a good (as in good performance) physics library that I could use in Java projects. The ones I found reportedly didn't work well on slower hardware.
The result is Java bindings (i.e. a JNI) to Chipmunk, the 2D physics engine. Below is a demo of it running a simulation on Android Dev Phone 1.
The bindings are far from complete, but I have decided to release the project anyway. Code can be downloaded or browsed from its project page at Github.
