Graffiti Research Lab, openFrameworks, The Fat Lab and The Ebeling Group have teamed up to create The EyeWriter, a "low-cost eye-tracking apparatus & custom software that allows people with paralysis resulting from Amyotrophic lateral sclerosis to draw using only their eyes.
" This instruction set details how to make your own solderless eyetracker for only $50 using a hacked PS3 Eye and a cheap pair of sunglasses.
http://www.eyewriter.org/