The Accessory Development Kit (ADK) allows you building USB or Bluetooth accessories that extend the capabilities of your user's Android-powered devices. Android defines the Android Open Accessory Protocol (AOA) used in accessories to create a communication channel between your Android application and your ADK compatible device.
Compatible Android devices
Android Open Accessory support is included since Android 3.1 (API Level 12), but a porting through an Add-On Library was available even in Android 2.3.4 (API Level 10). Check the official documentation for more information.
Even if your Android device uses an API level 12+, it doesn't mean that it is ADK compatible. The ADK support is related to some hardware specifications that your smartphone / board manufacturer should comply. Before you proceed, check if your smartphone or board have a full ADK support.
Compatible ADK devices
Your accessory should implement many features as described in building custom accessories section. Many Arduino devices have a built-in support for ADK (and so AOA protocol) and the following is a list of supported devices:
This list is community driven. There I will list only devices that me or other contributors have used. If you are pretty sure that other boards have this support, follow the contribution guidelines.