This project registers a portable moisture sensor to be used on the exterior (it's not water proof in the first iteration). It's battery powered and uses a tiny ESP8266 (Wemos D1 mini). Thus, it could be extended to automatically register data by using WiFi. Designed to be ergonomic using prototyping materials (so not very much...), it has an end of race swith to power up the device and another button to configure its offset.
Please, feel free to ask as many questions and add any suggestions. I'm glad to share and improve.