ProView XL35 at Kaiser Electro-Optics is the best head-mounted display I've read about, featuring full XVGA. I've wanted one of these things for 10 years, but most current consumer products are stuck at a worthless 640x480. There's an faq that covers HMD vendors. Turns out an XVGA HMD can run $35K+. Ouch!
Kyung-Nam Kim:Vision-Based Eye-Gaze Tracking is an early foray into a world where expensive eye tracking machines won't be required for low level usability analysis. A thousand more mhz or so, and a hi-res quickcam on top of the monitor ought to do it. All we have to do is figure out how to use the data!
An equally intrigueing scenario is user input via eye gaze. Some sophistication in user state modeling would be required. Finally, consider the thrill of marketing shucks being able to beta test their ads... ok, maybe this isn't such a good idea