Remember Nike's cool Chalkbot (a descendant of StreetWriter) that printed SMS messages for Tour de France cyclists on the road surface? Here's a similar idea: a drum of water, a stencil, and an ad message. Done in 1930 in Spain to promote a wine merchant.
And a modern-day "sea-tagging" campaign to promote an aquarium in London through sea-water prints on pavement:
A few other writing and drawing machines:
Hector the Graffiti Robot (from, like, 2004).
A wall-climbing printer.
PixelRoller (we wrote about it a few years ago).