I came across this video demonstrating a handheld wall printer. I think it is quite an achievement. It looks as though it calculates distance and timing based on the devices wheels, and uses solenoid stamps for printing.
TEXTBOMER from H@nnes at HfG on Vimeo.
However, I can not seem to find much information on the project. Only a few pictures from google/tech sites.
Know more about this project? Reply the designer's website.
Cabe
ps. The next step I would like to see is higher resolution and color.