As seen in the streaming of Google IO 2011, physical computing and interactive enviroments are one of the main topics opening the conference. The Android Open Accessory Kit is going to allow Android related devices receive data from different sensors (just via USB, for now).
The Android Open Accessory Development Kit (ADK) provides an implementation of an Android USB accessory that is based on the Arduino open source electronics prototyping platform, the accessory’s hardware design files, code that implements the accessory’s firmware, and the Android application that interacts with the accessory. The hardware design files and code are contained in the ADK package download.
The board is based on the Arduino Mega2560 and Circuits@Home USB Host Shield designs, since it communicates to the phone in its “accessory” mode. You can get the custom library / firmware to make it run & test with the shield pictured on top.