“Hunter Scott, a student at Georgia Tech, discovered a serial out on a Star Wars Force Trainer EEG toy, so he decided to make it into a musical instrument. When activated, the electroencephalography-driven toy plays a variety of samples depending the readings from the alpha and beta brainwaves.”

http://blog.makezine.com/archive/2010/05/mental_note_an_eeg_musical_instrume.html
http://hscott.net/projects/mentalnote/