I doubt you'd be able to get a signal through from inside the fridge. I made a Home Assistant "food safety" dashboard and alerts. I found two challenges:
* Connecting to the outside world. I didn't go wireless because a fridge/freezer cavity is basically a Faraday cage, because I didn't want to deal with replacing batteries, and because high humidity + low temp = wet, sad microcontroller. And even a "flat" 4-conductor telephone cord disturbed the magnetic seal enough that there was a noticeable gap. I ended up buying a 4-contact, 1mm pitch, 200mm flat flexible cable to run across the seal. I separated the contacts with a utility knife, soldering them to other cables on both sides. I also heatshrinked the conductors individually and the whole junction together for strain relief. Then I superglued it into place. And 4 conductors is enough for ground, supply voltage, and either TX/RX or 1-Wire+unused.
* Getting a reading that matches what foods actually experience rather than the air temperature. The latter fluctuates a lot more when you open/close the door or depending on what the defrost/compressor is doing. I ended up buying waterproof 1-Wire temperature sensors (elecrow sells them for $1.20 each + reasonable shipping), 4 oz plastic bottles, cable glands, and propylene glycol (relatively safe antifreeze, though I wouldn't chug it). I drilled holes in the lids for the glands to run the sensors in, then closed the bottles up while immersed in the solution. Cheap DIY buffered temperature probe.
I currently measure buffered temperature, air temperature, and humidity, but really only the buffered temperature matters.
* Connecting to the outside world. I didn't go wireless because a fridge/freezer cavity is basically a Faraday cage, because I didn't want to deal with replacing batteries, and because high humidity + low temp = wet, sad microcontroller. And even a "flat" 4-conductor telephone cord disturbed the magnetic seal enough that there was a noticeable gap. I ended up buying a 4-contact, 1mm pitch, 200mm flat flexible cable to run across the seal. I separated the contacts with a utility knife, soldering them to other cables on both sides. I also heatshrinked the conductors individually and the whole junction together for strain relief. Then I superglued it into place. And 4 conductors is enough for ground, supply voltage, and either TX/RX or 1-Wire+unused.
* Getting a reading that matches what foods actually experience rather than the air temperature. The latter fluctuates a lot more when you open/close the door or depending on what the defrost/compressor is doing. I ended up buying waterproof 1-Wire temperature sensors (elecrow sells them for $1.20 each + reasonable shipping), 4 oz plastic bottles, cable glands, and propylene glycol (relatively safe antifreeze, though I wouldn't chug it). I drilled holes in the lids for the glands to run the sensors in, then closed the bottles up while immersed in the solution. Cheap DIY buffered temperature probe.
I currently measure buffered temperature, air temperature, and humidity, but really only the buffered temperature matters.