You might be interested in this: http://www.eyewriter.org/[^] which uses a hacked PS3 eye wired to some empty glasses, open source software available here[^], could presumably be used with any other suitable webcam etc video source. On the commercial side, I've tried the headmouse extreme[^] which is expensive, but not prohibitively if you have a need for mouse replacement (my wife destroyed her wrists/forearms writing her phd thesis). It works straight out of the box (appears as a usb mouse), mounts on your screen and tracks a dot you put on your head/hat/glasses but did seem to lead to a stiff neck from precise head movement.