Nice project! It reminds me a lot of the course we did in 2006 with Matt Cottam with hacked keyboards and all. And keyboard emulators have been around for over 10-15 years for prototyping quickly interactive projects around key presses and such. It is a very rapid and ubiquitous way of controlling any software (almost).
http://www.ultimarc.com/ipacve.html
We have 6 of those in the Interaction Workshop. I’m not sure the school is ready to chip in for a Kickstarter pledge (legally it has issues), but once MakeyMakey boards are available via Sparkfun, I don’t see why we can’t stock a few a those at UID.
There is a new board apparently with mouse events capability: http://www.u-hid.com/home/index.php
/Camille
If you want to do similar switches (capacitive touch) with a stock Arduino, check this http://www.arduino.cc/playground/Main/CapSense
As for transforming an Arduino Uno into a generic USB device (keyboard, mouse, joystick, etc), check http://www.fourwalledcubicle.com/LUFA.php and http://arduino.cc/en/Hacking/DFUProgramming8U2