I always wanted an external thermometer in my car. I find it useful for ice warning and general information.
Unfortunately, my 1999 Citroen Xsara mk1 doesn’t come with one. I had to hack it.
I bought the Auriol Internal – External Thermometer from lidl. It has Ice alarm, min/max settings, and long 3m cable. Everything you need from a car thermometer. It only costs 3.99€. Sweet.