Wow, I love this.

This seems to be based off of an existing product, called the Tenori-on (or perhaps it's the other way around?). Anyway, it seems to work the same way. I heard of it last summer and instantly wanted one.

Here's an example of it: http://www.youtube.com/watch?v=-CWBgm_-Ggs

I'm going to be playing with this site a lot, thanks Sapphire.

Edit: The source is this: http://www.hobnox.com/index.1056.en.html, which seems to be a more complete version of it.