A free app for Android, by droidplant.

Bluetooth Power Saver is a small and simple application to save battery. When your device is connected, the app will keep it in that state.

It will only switch to an inactive state when your connection to the source is lost. It will not switch to an active state unless the connection is re-established. This ensures that the battery is not wasted.

It works as intended, but because of the Android platform, it is not possible to use it to turn off Bluetooth on more than one connected device at the same time.