The Flipper Zero is this idea on steroids: https://flipperzero.one/

I used to do this in the early 2000s with my Palm PDA's IR blaster http://hp.vector.co.jp/authors/VA005810/remocon/premocce.htm

UK superstore Tesco had TV's with adverts a few years back. I used to walk round the store with my WindowsMobile devices with IR and turn them off.

Always hated advertosing.

A FOAF connected a TV-b-gone to an array of high-power LEDs, enough to turn off all the TVs in a large shop from inside a canvas bag outside the entrance.

This, I think: https://www.timeexpander.com/img/extender2.jpg

I would have liked to borrow that and go for a walk ;)

Me too!

My dad gave me an old PalmPilot when I was in middle school and as a punk kid I would do things like mute the TV for 5 seconds during in-class videos.

Still have mine. Used it a handful of times. Mostly worked! I wish they had a similar device to eradicate music from restaurants and cafes.

Headphones (noise canceling, even!).

I was going to say that it was sometimes hard to hold a conversation over the music, but two people with noise-canceling earbuds would definitely up the difficulty. (Or we could just call each other.) ;)

That could work. But I hate it when the audio is even a little bit out of sync with the video.