Paging systems essentially work the same way, only with a bit more information and higher cost. And usually don't provide anything more informative than a missed call would provide. Why didn't we think of this sooner, rather than come up with specialized devices for everything?
The money-saving Asian stereotype isn't all too unknown – but this sort of solution would likely make sense in the west as well. A missed call (ring once and hang up) initiated automatically by a particular trigger (e.g. when a water pump is out of power) is sufficient to tell the user that something is wrong and they should check up on it. In case of water management, that it's time to start up an app tracking water pump power status.