I tried it, and it did not work all the time on re-start after a shut down. (water changes) Too scary for me if I were relying on it after a power outage. I hooked up my second one to a powerhead that I was already using in the tank any way. That works, too!
Note: I found mine for $15 and I may just buy it and use the power head as back up, if one breaks. (I also have other tanks with overflows using waterlifters.)