This was a little bit of a cheat. It just so happens that the computer being used for the Zoom calls is a Mac, so I just wrote a program that runs in the backg

This was a little bit of a cheat. It just so happens that the computer being used for the Zoom calls is a Mac, so I just wrote a program that runs in the background on the Mac and asks the OS about whether any microphone devices are in use by any programs, and then sends a message to the Pi, which really is only turning a hat of LEDs on/off based on UDP packets it receives. It could be turning the indicator on/off for anything that somebody else told it to do it for. (Originally, I was using an Arduino Nano and a USB serial interface for communication, but my flatmate rewrote it to go over UDP to a Pi Zero W, as he wanted to use a particular RPi hat as the indicator lights) Detecting the microphone on/off status on OS X was shamelessly ripped off from the answer to this StackExchange question: https://stackoverflow.com/questions/37470201/how-can-i-tell-if-the-camera-is-in-use-by-another-process https://stackoverflow.com/questions/37470201/how-can-i-tell-.... I don’t know if there’s a similar approach that would work for Windows or other OSes.