If you play tabletop games, with ww2 tank miniatures this utility can be very useful.
Panzer Combat II is a multi-player voice and webcam enabled computer-assisted distributed miniature wargame of World War II tank combat. Firing is done by placing a webcam behind the aiming unit. Distance to target is computed using computer vision. Action inside the tanks is performed on the computer screen while battlefield strategy is played on the miniature terrain. Both camps can use a different laptop or tablet, the game will interconnect.