Maybe this could not seem directly LEGO MINDSTORMS related, or even blasphemous to the purists, but the secret Android device published in a previous post is not a secret anymore!
Its name is Teemino, a device that can be controlled by an Android ADK compatible phone.
This means that your Android version should be 3.1 or 2.3.4 to have the Open Accessory support.
Soon also the NXShield will be available: it will allow the Teemino to control up to 4 NXT Servo Motors and read 4 digital and analogic sensors.
Here's a video to see it in action (impatient people should skip to 5:20)