Although this may sound complex, it isn't as difficult as first imagined. Created by Arduino forum member "wizard123", one side is a simple Android phone app that reads the handset's accelerometer - and sends the result to the Bluetooth port. At the Arduino side there is a cheap serial Bluetooth adaptor connected to the serial line - which receives the message from the phone and thus controls the tank. In the following video you can see it in action:
Apart from being a fully Arduino Uno-compatible, it has onboard microSD socket and the full USB socket and host-mode controller. As well as the Bluetooth application described above, this is the ideal platform for developing peripherals or projects based around Android devices with ADK (Android Developer Kit) functionality, but without requiring a USB host controller shield stacked onto an Arduino. For more information and to order, visit the product page here.