I got an email from Coastal Climate today (advertising) and it led to this unit on their website.
Guardian, compressor speed control and digital thermostat
While a bit on the spendy side, it might be a good upgrade for many of us with compressor frigs, assuming it is reliable.
I have sent an email to Coastal to see if they have an electronic version of the install and user manual for the unit. I hope they do, as it would answer a lot of questions.
It has a compressor speed control (we added a homemade one years ago), digital frig temp thermometer, and diagnostic LED that flashes error codes if there is a problem.
We have had repeated thermostat failures in our frig (3 in 6 years) and the wireless thermometers, while cheap, also need to be replaced fairly often, so could be good for us if it is low power use and has good adjusting range. It would require removal of the frig, it appears, to install, but that would also make it so the temp wire could be run through the current thermostat hole and not over the door gasket.
I had wondered for a long time why something like this wasn't around, and now it is.