This app has been made for an arduino kit available in Ebay (Kit arduino Bluetooth Android). This kit is composed of an arduino, a relay, a Bluetooth module and a conductive switch.
First is to pair your phone with the Bluetooth module. Once paired it has to selected form the available devices.
Once the device is paired and selected the phone will received the status of the relay (light for example) and will update its status (on or off).
You can change the state of the relay from the phone. The status of the relay can also be changed through a conductive switch to turn manually on or off the relay. The new status will also be updated in your app.
The app also plays the sound on or off of the current status when the this changes.