On the heels of the Korg Cliphit, a gadget that transforms anything (yes, anything) into a drum set, some former MIT students have designed a device that turns bananas into a piano or keyboard. With room for 18 electrodes that you can push into bananas, pencil erasers, potatoes, or anything that can conduct electricity, you can program the Banana Piano to play your computer's piano or do other less-useful things.
How about a stair piano? Water foot pads? Graphite scribbles? Yes, yes, and not a problem.