Do Androids dream of Electric Sheep? Well if not, they should. The Electric Sheep board is a development tool (similar to the Arduino Mega ADK) for creating custom Android accessories. Based on the ATMEGA2560-16AU and carrying the same bootloader as the Arduino Mega 2560, this board communicates with your Android device over USB by taking advantage of Android's "Open Accessory" protocol. Android device-side interfaces can even be created without having to write Java code or mess around with the Eclipse IDE by using HandBag for Android!
Note: Because of the configuration of the Open Accessory protocol, this board needs to supply 500mA to the Android device over the USB connection. If you're running peripheral devices from the board, you will need to provide more current to the DC input, which is rated for up to 1.5Amps.
More info at SparkFun
This product has been discontinued at SparkFun.