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 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 something like that? obviously not exactly the cheapest thing in the world, but, it gives you an idea of what would be required