Could your PC serve you better by knowing its position relative to you? Ubuntu interface designer Christian Giordano experimented with the concept last week, and he has an interesting video to show for it:
Giordano says his colleagues at Canonical thought of several ways to improve the user experience by making the PC more physically aware. Moving away from the screen with a video playing back, for instance, could make the video fill the screen. Similarly, notifications could take up the whole display when the user isn't sitting right in front of his PC. As the video shows, a neat parallax effect is also possible—although I can't be the only one to think that might get annoying after a while.
Giordano's experiment involved his PC's webcam, but he says user-tracking technology could use infrared or ultrasound sensors to do the same job. You wouldn't want your webcam light to stay on all the time, right? Not using a webcam could circumvent unintentional racism, too, which is always a plus.