I have been working on a senior project that involves communicating an Arduino board to a phone. Now I was going to use the Arduino ADK but because of dimensions issues I have to make my own print circuit board. I have been comparing these two boards and found that the Arduino has an extra microprocessor. I didn't know what its purpose is for and was hoping someone could help.
Arduino http://arduino.cc/en/uploads/Main/ADK_MEGA_2560-Rev2-sch.pdf
Electric Sheep http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Android/electric_sheep-v11.pdf