Project Mimicry, an indie concept piece for Kinect, is a sandbox game in the truest sense of the word: it uses a real box of sand as the game's controller.
There's currently not much game to the project, developers Monobanda content to instead let players build their own experiences making things like obstacle courses or race tracks.
Project Mimicry works like this: a Kinect camera watches a box of sand. Players mould the sand into whatever shape they desire, and the resulting form is generated in the game as a level.
There are a few neat touches to Mimicry, like giving tall "mountains" snow and turning recesses into lakes. Everything's still in the very early stages, so there's not much to go on than that, but you can check out how it works in the clip above.