The way I've been able to learn that devices are off since the early 2000s is that the blindingly bright blue LED light is replaced by a blindingly bright red LED light.
I really hate those. When your house is dark and it's calm and all you see are little eyes of Sauron floating in the darkness. I've gone around my house with masking tape and covered every unnecessary visible light.
Google Wifi is one of the worst offenders. They might as well market it as a wifi-repeating lamp.