Just a short post on this, too cool to not share for those who haven't seen it. Make music with tangible items. This is pretty cool stuff. Although it is not currently available commercially it is being used and I am sure will take of in a year or two. They provide the software to interface (GPL), but not all the pieces you will need.  They also provide instructions to build your own table. Looks to be a pretty involved process, but could be fun and well worth it when you're finished. 

Visit the Reactable web-site , they do live shows so take a look at their schedule while you're there.