How to make a cheap heads-up display (HUD)

It may be intended as a toy, but this gizmo can be hacked for more than just watching a remote-controlled car's video spy cam. This HUD (heads-up display) comes with the Wild Planet Spy Gear Video Car, but it's said that you can purchase the video headset separately. And it's not really a HUD, because you can't see through the video images, but it's close enough to be handy for all sorts of things, like computers, iPods, robots, wireless cameras, and gaming. Who wouldn't like to Call of Duty with this thing?