Aaron Waychoff of DINO Studios came up with a simple way to create an iPad Physical Object Interface. Taking advantage of the device’s multitouch display, he created a set of devices with unique footprints that can be set on the display. Because the feet are made of a material (damp sponges stuck in the fingers from latex gloves) that can be picked up by the display, he was able to write a software algorithm to detect the presence and identity of each object that was placed on the screen.
Once he had it working, his collaborator Emily built some plant creatures out of them. Cool stuff!