Here’s a tutorial to set up the Network UPS Tools (NUT) binding with a compatible UPS.
As @Bruce_Osborne noted, openHAB doesn’t actually need to do anything…NUT does all of the work to monitor the UPS and shut down the RPi if necessary. However, the binding enables you to keep tabs on it. I have my wifi router and modem also on the UPS, so that openHAB can send notifications to me via the Android app (power is out, power is restored, shutting down Raspberry Pi).
