With thanks to Faye Simpson, I'd like to introduce:
This is a mouse controller for people who cannot move their hands well, but have control over head movement. It is free and uses a web-camera and head movements to move a computer mouse. It should work with any Windows program. For more information, visit http://cameramouse.org/about.html.
Faye suggests that it could also have uses in adapting tests such as blocks, Rey Figure or Wisconsin Card Sorting Test for people who do not have hand control.