This is absolutely amazing. I really want one. For more info, see their website at http://mtg.upf.edu/reactable/.

http://video.google.com/videoplay?docid=-4689008057039304357

Two more videos if you liked this one.
http://video.google.com/videoplay?docid=1179567625633117422
http://video.google.com/videoplay?docid=-6097905637135414804