Two-fingered salute

Toshiba is making computers that respond to hand gestures. Eight
light-emitting diodes on the PC flash infrared light at 50 hertz while a lens
and motion detector pick up reflections from the user’s hand. The motion
detector is programmed to ignore low-level reflections from the background but
respond to movements close to the screen. The computers are now being taught to
recognise sign language.