Bluetooth relay to control water pumps, lights, etc

Is there an inexpensive way to control a water pump or light or other device needing only to turn on and off by using bluetooth?  What I see in my mind....is either a computer or tablet having a bluetooth sender - either built in or a usb dongle...and, for example, an aquarium water pump with a 3.7 or 5 v relay to turn it on and off coupled with a bluetooth receiver.  The computer or tablet would have an app to control the device - with timer software.  I have seen bt dongles that can be purchased for as little as $2 in bulk...low voltage relays also for cheap.  I envision a "box" about 1cm by 3 cm by 3 cm that a pump or a light could be wired into and costing about $US 5 to make.

There are various Ibles that spring to mind. There's one for a "garage door opener" and a "door lock" - the hardware is the same, its just what you're connecting it to that changes.
crapflinger4 years ago
http://www.relaypros.com/Relay/Relay/CAT_RELAY1_BLUETOOTH#.UV7cNxfD-M8 something like that? obviously not exactly the cheapest thing in the world, but, it gives you an idea of what would be required