Gizmo’s new PFA-3 Power Monitor will monitor three-phase power for over-voltage, under-voltage, asymmetric voltage. If the voltages are not correct, of it there is a complete power failure – a loud alarm is given.  

The alarm can be silenced with the pushbutton for 30 minutes.  (this is the default behavior which can be changed)  The battery will store passively for 10 years, and will support an active alarm for 4 days. There is also a low battery alert if the voltage runs low.   Product page for the PFA-3 which includes video.