Since I've started automating stuff I've got myself an Acurite wireless fridge and freezer thermometer (initially found out about it on Reddit, before it all went to shit and all). It both has a nice magnetic display and it transmits in 433MHz band, so a SDR dongle plugged into my Home Assistant machine can receive the temp readouts. So far it didn't prevent any disasters, but at least I know how hot it needs to get for the fridge to start having trouble keeping cool.