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.