GridWatch is a system for monitoring the state of the power grid using just smart phones. Phones running the GridWatch application monitor their status for power change events (when the phone goes from charging to not charging). This transition could signal a power outage, but is likely just the user unplugging his/her phone. To determine which, the phone checks the accelerometer for motion (signifying the user is picking up the phone), and the microphone for evidence of a 50/60 Hz signal emanating from the power grid. If neither signal is detected, a power outage event is transmitted to a server. These events are aggregated to detect a power outage.
The .apk for Android is located in the /release/android folder.