Of the various ideas I have been prototyping, one showing some promise is Block Rockin’ .. it’s a 3D Arkanoid or Brick-Out type game controlled by physics. Using the tilt sensors on the iPhone is a great way to control it too – your bat moves around a circular platform. The blocks are destroyed after a couple of strikes, but they also tumble about and (if they’re in a wall or henge configuration) you get quite a pleasing level of destruction.