The pump monitoring stuff I set up (basically a z-wave switch that reports current draw to Home Assistant) seems to work perfectly! When operating correctly the pump draws current in a relatively narrow band, so I have an automation to turn it off if the draw is outside the expected range (which might indicate that all the water has fallen out), and also gives an indication of whether there's a leak anywhere (if the pump is turning on without any water being used, that's a bad sign)