For decades now drivers have been been using the horn signal and shouting to let each other know what do they think of each other. It works very well provided your your horn works and/or your side window is open.
There is a company in UK (it seems) that thinks that there is a need for additional methods of communication. TextJam provide a service which you can use to SMS exercise profanity via discussing traffic situations. It is, of course, difficult to quickly find some other driver’s phone number, so TextJam does it a bit different. You send your message to TextJam indicating the license number from the plate of the car you want to contact and they forward the message to the appropriate mobile or email address. The other driver should be using their service too, though.
The idea is all interesting and original. The only thing I am not sure about is how they will diffirentiate between driver’s who have identical number plates in different countries. I am pretty sure that is possible…