That sounds pretty cool! And sure, feel free to ask about my systems - a lot of the stuff is already up in the hgpstools repo. For the CO2 logger on my list above, I've been considering combining an Arduino with an RPi, where the Arduino does the data logging and the RPi is only woken up to do the WiFi user interface, to conserve power while it's deployed in the field doing autonomous measurements, but I haven't fully decided on that set-up yet - but now that you mention it, the ESP8266 NodeMCU looks pretty interesting too!

Do you use any solution to monitor multiple RPi's, i.e. whether they're still on-line and sending data regularly etc? That's an issue I'll probably have to tackle eventually, as the number of RPi's (and other measurement stations) I deploy grows.