Background: The Watterott CO2 Ampel ("CO2 traffic light") is a networkable sensor board, primarily made for monitoring CO2, but includes other sensors as temperature and humidity as well. It is open hardware and uses an open source firmware. https://learn.watterott.com/breakouts/co2-ampel/
The factory firmware includes a simple Checkmk agent via HTTP/REST-API: http://12.34.56.78/cmk-agent
Since the agent is only available via HTTP, the monitoring has to be configured using "individual program call instead of agent access", see
https://docs.checkmk.com/latest/en/datasource_programs.html
The output includes one local check that creates a service immediately after discovery. However, this takes thresholds from the EPROM of the boards which makes central administration difficult. This plugin adds discovery for all other sensors. Since different versions of the board have different sensors, individual discovery is needed.
German users: See ASR3.5 and ASR3.6 (Germany) for thresholds on CO2/temperature/humidity in working environments. Only CO2 is quite fixed at 1000ppm. If no quick exchange of air is possible, lower thresholds from 1000/1200 to 900/1000 or properly adjust the hysteresis.