Temp Sensor for Scientific Freezers

I'm designing a low-cost temperature sensor to be used in extreme-cold freezers (-80°C). This device is Arduino-based, so all components and many of the necessary libraries can be easily obtained online - Adafruit is a great supplier that provides a lot of fun resources and quality support at a price that feels more than fair. Here the device is reading my kitchen freezer to be -12°C, which seems about right. What's nice about the breakout chips used is that it also takes a temperature reading from the location of the circuit - more on that later.

I ultimately want to incorporate a wifi breakout module so the device can send an email to the user if the freezer heats above certain temperature thresholds. One tricky aspect is that the majority of readily-available (and affordable) integrated circuit components are rated for temperatures -40°C < x < 80°C. That means instead of using the more common Arduino-friendly temperature sensors, I would need to incorporate a thermocouple - rated for much wider thermal extrema. That takes care of the actual sensor, but the rest of my circuit will still be susceptible to these extreme temperatures - which leaves me with two foreseeable options (but open to suggestions!):

1. Mount the device on the outside of the freezer and route the thermocouple to its interior. In this design, I would also be able to incorporate the LCD to display live readings.

2. Make a self-contained housing, probably sealed and thermally insulated, with a few resistors in the circuit that turn on if the internal temp drops below something reasonable (like -20°C). Thats where the integrated "interior temp" reading comes in handy. I'm not sure how much power the "heaters" would need in a constant -80°C environment to maintain a cozy internal temp, but battery life could become an issue here.

I'll update this post with any new developments.