I don't have the technical savvy to link this--if it is linkable--but if you go to Page 16 of the April 9 New York Magazine, you can read about and see the bike Joshua Kinberg created to demonstrate at the Republican National Convention.
It was quite brilliant: his master's project at Parson's.
You would call in a slogan you wanted printed on the street and, in real time, out it would come, neatly printed in chalk.
Needless to say, the NYPD swept him up and arrested him before he was able to put it into practice--the result of the NYPD's black bag op of surveillance.
Remember to pay your city taxes.