Since Arduino can be programmed to function as a keyboard[1], wouldn't that be an easier option? Then you can put the chording logic on the Arduino board and have it function like a plain USB keyboard otherwise as far as the computer is concerned[2] (that's kind of how the Makey Makey[3] works - it's also Arduino based).
Yeah, you should be able to do that as well. There are a lot of different ways you could make a project like this work, I was just wanting to throw out an example to show that we're empowered to do these kinds of things now. We don't have to wait for some company to come out with a portable, bluetooth chording keyboard anymore, we can do these kinds of things ourselves. I think that is really exciting!
[1] http://arduino.cc/en/Reference/KeyboardWrite
[2] http://store.arduino.cc/index.php?main_page=product_info&cPa...
[3] http://www.makeymakey.com/