Project to use Puck.js as a Remote Temp Sensor (Eg To monitor fridge/ freezer)

Strange error - can you post an issue on https://github.com/espruino/EspruinoTools with the exact contents of the file that wouldn't upload?

But I'd say the setAdvertising method you'd used is best for low power since it doesn't need a connection. This might be a good way of getting the data into your Pi: http://www.espruino.com/Puck.js+Node-RED

And most likely it'll be the battery that won't take freezing temperatures, rather than the Puck - you might be able to find a special CR2032 meant for low temperatures I guess