Natural Point in Corvalis, Oregon (www.naturalpoint.com/smartnav) makes an excellent device called SmartNav that tracks a small reflective dot on the forehead. The manufacturer's suggested retail price is $399. Contact me for a possible much lower price.
Using the SmartNav takes some practice, like any motor skill. Here is some useful advice on adjusting it. Unfortunately, not everyone can master the SmartNav well enough to use Sue Center. Given the substantial benefits, however, it is certainly worth a good try. Motivation is all.
One fun way to practice controlling the mouse is to play the Match game.
If you wish to use the SmartNav to access other programs you will need to be able to issue clicks and double clicks and drags. Natural Point does sell a more expensive AT model (other than the $399 standard one described above) which includes a dwell clicker that works with the SmartNav camera. If you'd like to save that expense (who wouldn't?) you can download a free open source dwell clicker from Sensory Software International here.