http://monome.org/
this is so great! be shure to watch the video:
http://monome.org/media/monome40h.mov
I saw something similar developed by yamaha and shown at ars eletroncia 05: tenori-on
www.global.yamaha.com/design/tenori-on
To make something similar...
You'd need:
4 - "4x4" Digital LED Display ($19.99/ea)
1 - Multiplexer (for inputs) - Like the one on the punching bag, that had 64 force sensors
1 - Matrix LED control (for output LED's, nevermind dealing with colours...)
64 - Tricolour LED's ($1.79/ea for 10+)
Oh, and of course, someone passionate enough to write code for it.
... man, why am I getting tempting thoughts right now? Oh, wait, I still suck too badly at coding to do this.
Anyone wanna take a jab? It's doable...
(I'd probably pay about 100-125$ for one.)
their code is open, and they are selling small quantities of the pcb too
Happy New Year
Nick