I bought an inkbird unit. (https://www.amazon.com/Wireless-Thermometer-IBS-P01R-Floating-Connection/dp/B0B1DLKHJD/ref=sr_1_32?crid=3AY8PB7ZPNBID&keywords=inkbird&qid=1674771734&sprefix=inkbird%2Caps%2C105&sr=8-32)

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It doesn't alert, but it does run on batteries and bluetooth so wouldn't die with power outage. It has helped a ton when the cover was left askew or the spa heater stopped working. We put it in early November and have changed the floater's battery once, just recently.