PowerManager is an Android application that detects if your device is being charged. The ringer, Bluetooth, GPS, and Wifi states can all be configured when AC power is connected/disconnected. For example, it is possible to change the ringer to be on while charging and go to vibrate when not charging. This is also useful for saving battery as well since Wifi and Bluetooth consume a lot of battery. A simple configuration screen lets the user customize the settings.
Also, Google Voice phone numbers can be enabled/disabled when AC power is connected/disconnected.
The application was designed to use as little battery as possible since it is running as a service. The service only runs when a power connect and power disconnect event is received.