I'd be lying if I didn't admit that this one creeps me out a bit. A green PC maker out of the United Kingdom (VeryPC) has rigged some facial detection software to work in conjunction with your system's power management features. As in, if the software doesn't "see" that you're in front the screen, looking at it, it will kick the computer or the display into sleep mode.
The software, called PecoBOO, works by keeping its own digital eye out to see if you're looking at your screen or not. (So it obviously requires a digital camera hook-up.) It hooks into the existing power management software that's already on your computer, turning off the screen when no one is looking at it. By the same token, if you're looking at the screen, it WON'T turn it off, which can be annoying if you've been doing something that hasn't required you to touch the keyboard in a long time. Poof, you're reading away and the screen goes blank.
VeryPC says the software doesn't log the activity or act as a security beacon ANYONE could be looking at your screen in order for it to be working, just as long they're in the area the camera is watching.