Implementation through PlayStation Eye may be difficult because you need the camera to recognize the face (and most specifically the eyes). Xbox 360 was going to use two cameras, that may be another option.

I managed to get my light pen successfully built. Another tip in the building is that cameras can often see IR lights; interestingly my cell phone camera (SE W600i) and my friend's (Moto Razr2) were able to clearly see the IR light cast, letting me see if it was actually turning on. Of course, an adjustable power supply with built in ammeter also helps .

The only problem I'm having is with the intensity of the light and getting the Wiimote placed close enough to have proper resolution and intensity (the farther you go out the harder it is for it to see the LED), but far enough away to reach the corners of the projected screen. Today I'm going to try with a tripod to see if I can get the ideal position.

EDIT: another interesting note is that for some reasons the Dell LCD monitors I have are very reflective to IR light -- interesting because they don't reflect visible light. But as a result, I'll bet that the touchscreen concept would work very well on an LCD although I haven't actually tried it yet.

Not the line of sight, but the eyes relative to their eyes. I think the video example works very well because the sensor bar put below the camera does full eye-tracking, same as the glasses with the lights or the goofy cap. The point of vision is different if you are perpendicular to the TV screen at a corner or looking at the TV from the same corner.

My vacations begin either next Monday or the Monday after it (haven't yet decided which is better), I may (big MAY there) try to do something of this.

He has been interviewed by Game Informer, a pretty important gaming magazine. Didn't want to create a new topic about this, but it is worth mentioning it.