Hi
It works by infrared light picking up reflections from the clip piece. I have the regular one that attaches to a baseball cap.
Yes, you move your head while keeping you eyes on the screen. But your head movement is much less than the effect, so it isn't like you have to look out the corner of your eye to still be able to see the screen.
Yes, it will work with multi monitor setups.
Yes, it is usb.
Yeah, nearly every sim now supports it fully.
$129.95 for the one with the ball cap clip.
You can find out more at
NaturalPoint.
Be sure to check out the videos

If you decide you want one, you can get a $15.00 discount by using the banner ad over at SimHQ. Well, I guess that offer still stands. I bought my TIR 4 a couple months ago through the banner and got the discount.
IMO, it is a must have for any serious race/flight simmer. I have been using it since the first one came out in like 2001 or something. I worked really hard at getting support in race sims back then. Funny, many thought I was crazy and said it wouldn't work in a race sim. Well my vision wasn't blurred and I knew it would be great in race sims. I finally got Gjon Camaj over at ISI to look into it.
Now it is a standard in nearly every race sim

Even the game Test drive Unlimited (for PC) has full support for it.
Most of us that use it will all say, we won't drive or fly a sim without it. It becomes that necessary. Just like a joystick or a wheel.
You can even use it in shooters too, but I never really tried it in one. I did mess with it some in Morrowind, but not long enough to get used to using it in those type games.
Oh yeah, it doesn't put any real strain on your system.