Same as described in the various freezer projects, it all works well. 
You buy the probe separately, it’s just a dumb analog probe. You attach it to a smartthings compatible device which can read the probe, I think most people use Fibaro, they have two or three different models that will work.
I know people are still using this DTH:
'Fibaro Z-Wave FGK-101 Temperature & Door/Window Sensor' Full Support Handler