One option could be using something like an RPi and Domoticz or Home Assistant along with your RFX. Both of those could output to MQTT which could then be consumed by Hubitat via one of the MQTT Apps (e.g. [Beta] MQTT beta 3d (released 5th July))
I also have RFX and use a similar route for integration. I only chimed in on your question as you mentioned the TFA 30.3163 ..... I bought one recently to test for use in a freezer and it seems to read +40°C high. It does seem linear though, so with an offset it should be OK. Does that match with your experience?
