Ok, so my quick and dirty capacitive sensor is not very successful. Maybe it is that it needs temperature compensation, maybe I am just measuring noise. The biggest problem is that I do not know.

So time to collect data. I have bought a ESP8266 board and a sensor version of the Chirp. So I am probably connecting these as a (temporary?) logging solution and send everything to thingspeak or something similar. If only I had some time the next few weeks to put it together.