Yes, thats what you might have seen if you had bumped into McDonald's innovatively done Bus Shelters in some parts of the world. A steam machine was built to fit inside a transit shelter and periodic bursts revealed a message during a free coffee promotion at McDonald's. This is nice example of smart choice of media as it talks to consumer in a mood when she is receptive to the message....travel and coffee! Only if they had managed to push the aroma of coffee along with the steam it might have delivered a few impulse purchase from customers at the nearby McDonald's outlet.
Heres another innovative way of showing the same message.