Munin is a graphing and monitoring tool that is normally used to monitor servers.
Due to the very comfortable plugin interface the software is also very suitable for plotting all kinds of values from the environment or the internet.
As the operator of a large number of Freifunk nodes, you would like to keep an eye on the number of registered users. This plugin downloads the nodes.json from the map of the local community (in my case Freifunk Hannover) and parses the user count for all own nodes.
HomeMatic power measurement
I have some HomeMatic radio sockets of the type HM-ES-PMSw1-Pl in use. These sockets regularly report the power consumption of the connected devices.
HomeMatic temperature sensor
This plugin plots the temperature measurements of various HomeMatic devices such as heating valves, outdoor sensors and wall thermostats.
TFA CO2 sensor
TFA offers CO² sensors with USB interface, which report to the computer as a HID device. I updated an existing Python script to Python3 and converted it to a Munin plugin. This allows you to effectively measure the quality of the indoor air and you get a much better feeling for when it's time to open a window.