The expansion board is called the Gertboard, and is being developed by Broadcom employee Gert van Loo in his spare time. When completed, it will allow Raspberry Pi owners to play around with flashing LEDs, electric motors, and a range of different sensors. It effectively takes the $25 Raspberry Pi beyond just being a very cheap PC.
There's a video of the Gertboard already working which demonstrates the 12 LEDs being lit up and the board powering an electric motor more than capable of lifting something like your garage door.
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