There was a guy who sold a chip for that which you fitted to a car keyfob. In the olden days of the late 80s, Valeo used a pretty insecure not-rolling-code infrared thing for central locking systems.

Anyway you'd get a handful of old Rover, Peugeot, Renault, or Citroën (and a bunch of others) fobs from the scrapyard and fit this pre-programmed PIC microcontroller, and when you pressed the button it would cycle through a bunch of volume down, mute, and power off commands for most common brands of TV.

However the real genius one - and it was about 20 quid - was this. Remember Furbies? They would chatter away to each other, using infrared to communicate so they'd go in sync. Well, this one that transmitted the "GO TO SLEEP RIGHT NOW" command to any Furby in the room. Relatively expensive but worth it.