Weather Station => Special Sensors => #2
already allow for Minimal, Average or Maximal values from 2 sensors.
My suggestion is to allow a further option for Difference.
This would make it easier to plot and study differentials between sensors, for example if studying the effectiveness of insulation.
It would also allow someone with a "Temp in a Jar" solar to plot the difference, and thus get a better impression of the "shape" of that through the day (and night). I realise that "Temp in a Jar" is a very crude measure of cloud cover - but it is all some of us have.