After having our Norcold fridge fail on us (fuse blew on the DC heater) during a long slog up the coast on a rainy Thanksgiving (fortunately all the leftovers were in another ice chest!), I decided that I needed a way to monitor the fridge temperature remotely. I found that Engel (makers of electric coolers) have a remote temperature accessory - product link that looked to be a perfect solution.
For my recent month long trip to Peru*****, I needed to keep certain medical supplies between freezing and 46 degrees - so monitoring the temperature was critical.
There is a remote sending unit that I mounted on the inside “roof” of the fridge (no photo).
The unit uses AAA batteries, and they will last you for MONTHS of 24⁄7 operation. The unit could use a backlight for nighttime, but I don’t mind the tradeoff for long battery life. It also displays the time and ambient temperature.
The remote connection was “lost” only 3 times during my trip - twice I feel it was due to the iPhone located nearby starting up in the AM. Repairing the connection requires removing the batteries from both units, then installing the batteries FIRST in the receiver, THEN in the remote. This also requires stepping through the menu to set the time and choosing Centigrade or Fahrenheit, but that process is simple.
This should be standard equipment with all fridges.