Enthusiast Mario Böhmer has published a method to control AC mains sockets safely and remotely using an Android phone and Arduino. instead of attempting to rewire the mains sockets he simple hacked into the remote control for some remote-control mains outlets, and has the Arduino digital outputs tapped into the remote buttons with optocouplers. Then the Arduino listens via serial to a PC for text sent by the Android phone - which runs a custom app to simply turn the outlets on or off. For example:
If you're looking for an Arduino-compatible board with inbuilt USB host shield in order to experiment with the Android developer kit, look no further as we have the Freetronics USBDroid board:
Apart from being a fully Arduino Uno-compatible, it has onboard microSD socket and the full USB socket and host-mode controller. As well as the Bluetooth application described above, this is the ideal platform for developing peripherals or projects based around Android devices with ADK (Android Developer Kit) functionality, but without requiring a USB host controller shield stacked onto an Arduino. For more information and to order, visit the product page here.