Just caught a couple videos on Dutch site gerbster.nl - here's one of some Desktop VR using Papervision and WiiFlash to perform head tracking for a flash application -

Virtual Reality Head Tracking in Flash from gerb on Vimeo.

See their entry about it. Also check out their demo video of head tracking with a webcam instead of wii remote - the videos illustrate it pretty nicely.

Both are a little ways away from being widely usable - they use an external program to do the tracking (WiiFlash or gerbster's webcam equivalent) and serve the position through a local web server, but as Flash versions get faster, there's a real possibility of it all being done in the browser.