Once the Google ADK was announced, the team over at [ElectFreaks] jumped right in and started experimenting to see what they could do with the new Arduino/Android interface. While the ADK was great for allowing the two devices to interact over a USB connection, they felt that the system would be far better if it allowed for wireless communications instead.
They added a Bluetooth Bee to their Arduino setup and got busy writing an Android application that uses the handset’s built in Bluetooth module to communicate using the ADK. The application configures your phone to act as either a client or server when pairing. This does not affect data flow, as communications are bi-directional, it merely decides which device is placed in discoverable mode.
As you can see in the second part of their post, once the phone and Arduino are connected, it is quite easy to send serial data back and forth between the two devices.
As of right now, their Bluetooth API is in Beta, so things might still be a bit rough around the edges. They do encourage anyone to download and modify the code, which is freely available on their site.