About the only thing you could do to a kettle is make it switch off 1 deg cooler or something.
Toasters, well there’s a big gaping hole at the top. Capture that heat to use for something else, or use some kind of laser device than can spot cook the surface of you toast?
Hair dryer, just turn down the heat a little bit, and have a more efficient blowy motor.
Sounds nearly as silly as the day that UK “changed” to 230V AC +/- however many percent, instead of 240V. Remember the papers and BBC news saying how long extra it would take for kettle to boil. the voltage didn’t actually change. As we proved a long time after by sticking a multimeter in the mains socket.