TV Tuner

From Sega Retro

The TV Tuner plugs into the cartridge slot of your Game Gear, turning it into an LCD colour television. It has both antenna and mono A / V inputs, so you can use a VCR, camcorder or another video game console via the A / V. Because of the short battery life of the Game Gear (under 2 hours), it doesn't make a particularly good TV, unless you also have the AC adapter.

http://www.studio42.com/vidgame/GameGear/tv-tuner.jpg