geyserwise controlls the hysteresis curve of the element ,cutting down on waste of power by heating correctly and being more accurate ,it also prevents excessive loss of water out of the t.p valve due to overtemp at the end of every mechanical heating session ,so i dont know how you can say its useless ,do you know more than the manufacturer somehow .a normal geyser can leak up to 10 ltrs of water per day on a mechanical thermostat thats roughly 2 full reheats over a month and probably 9 kw minimum ,sounds like a good deal to me and the hundreds that ive installed since 2009