Edit: Also, http://johnnylee.net/projects/wii/ , under "Head Tracking for Desktop VR Displays using the Wii Remote" (down a bit).
(Also, to be clear, I just mean these as interesting "see alsos". I am not saying "it's been done" (so what?) or "it doesn't work" (I have no direct experience to make a judgment). Nor am I saying anyone accused me otherwise. The iPad is still a potential interesting sweet spot for this tech.)