I have learned that both the Onkyo TX-NR609 and TX-NR646 AV Receivers have a neat little protocol called EISCP that can be used to command them to do a bunch of stuff

All I needed was this python code here and to run it with

https://github.com/miracle2k/onkyo-eiscp

python -m eiscp.script --args-here

and I was able to turn my receiver on and off from the command line!

very neat.

It does, however, remind me of smart toilets, and I don’t really need to recreate that here from first principles.

You can also connect to the ’network control’ port via telnet and watch it print stuff out whenever the volume changes or other events occur

If these speakers were in any regular use in the house, I probably would find it convenient to have a Sonos device plugged in to them, and to have a computer in the house watch for active media being played to this Sonos device, and subsequently turn on the Onkyo amp so it’s “off” when it’s not being used. A future project, perhaps.