Shields are boards that can be plugged on top of the Arduino PCB extending its capabilities. The Arduino is also capable of sending out a video stream to your TV over a yellow component cable. So here is how I made my own Composite video-out for Arduino under 15 minutes.
Currently, the output is NTSC or PAL at a resolution of 128×96 by default. The library currently works on ATmega168,328,1280,2560,644p,1284p,AT90USB1286 and more can be added by editing one file.