The document discusses using Arduino boards with Android devices through the Android Open Accessory Development Kit (ADK). It describes typical applications that combine the capabilities of Android phones and Arduino boards, such as lighting control, body monitoring, and door sensors. It provides an overview of how the ADK software libraries allow Android and Arduino boards to communicate over USB or wireless connections. Examples are given of sensor and monitoring projects created with ADK, including an orb display, soil probe, and car monitor. Alternatives to ADK called IOIO and Amarino are also mentioned.