Well thats because its not easy to capture the movement from the Wii controller not to mention the other hardware you would need. Its not like the guy put the WiiMote on his head and voila it worked... Theres more then just the WiiMote and sensor bar and stuff...
actually I think it would be fairly easy. I've worked with Wiimote tracking some and when I get some free time I was thinking of implimenting it for LFS
I wouldn't mind seeing the Wiimote TrackIR but I haven't dealt with the any of the tracking details... I hope you do it well and let me know if you do end up doing it what I need and how to set it up . As far as using the wiimote as the steering wheel, that would kill it as a Sim since I have the G25, although I do suppose for mouse and keyboard users that would be very useful.
(Offtopic for the thread, but not too far Have you got a Wii yet? If not go get one! Really, no joke. Games are not about the pretty graphics millions of triangles and all the junk that the PS3 and XBox boast about. It's about pure entertainment and the Wii is by far the best at providing a very unique and fun experience that is worth it!