DS18B20 are the sensors you wanna get.
Current Status:
Debating trying, if I can find one… this: https://www.amazon.com/Fibaro-857934005119-Modern-Window-Miniature/dp/B00P2QAR8C/ref=sr_1_1?ie=UTF8&qid=1454770512&sr=8-1&keywords=fibaro+door+window+sensor
And this wired to it to go into freezer: HiLetgo 5pcs DS18B20 Temperature Sensor Temperature Probe Stainless Steel Package Waterproof 1M https://www.amazon.com/dp/B00M1PM55K/ref=cm_sw_r_cp_api_glt_i_JWWN93EYEHEKG81AQB56?_encoding=UTF8&psc=1