Using a webcam, some cardboard, and a bag of Skittles, [Kyle McDonald] created this tangible interface for a beat sequencer. The Skittles are dropped onto the rows which correspond to a drum channel and each Skittle represents an 1/8th note. For such cheap components, the system seems to recognize the sequences pretty quick. This is probably due to some clever programming with the processing back-end. He claims his inspiration was the BallBearing sequencer, which uses the ball bearings as contact switches to determine the sequence rather than having a webcam analyze the surface.
It would be really nice to see this project expanded into a full blown instrument. the webcam could allow for dynamic surfaces and he could certainly add more control to the system with some knobs and/or sliders. He claims these features, and the source, will soon arrive.