TV Tuner
Before the world cup last year, I bought a TV Tuner from Elgato. The Hybrid. This USB device does not need external power and provides access to digital radio and digital TV at standard definition in the UK. It comes with the EyeTV software for the Mac. Using this I can record TV Programs for playback later on either on my Mac or my iPhone.
In addition it has support for the Elgato Turbo.264 HD. this is another USB device that contains a processor dedicated to performing transformation of video into the h.264 format used by apple and other products.