Message the Irritating Driver Behind You

Why?

You know the situation: you have an irritating driver behind you, and you would like to let them know how you feel 😉

How?

Have a string of LEDs connected to a motor and a controller, stuck of your back window (maybe with a suction cup), that you can activate from your phone by pushing one button (of a few you prepared in advance) with the right message. The motor will spin up quickly and show the message for a short while.