Surely an actual inkjet ripped from a printer could be tied to the heel and driven off a small wearable platform with battery. Just a little bit of software with some of the acceleration sensors available on those boards should enable you to tell when the foot has been planted and squirt out a glyph from the inkjet. see Adafruit, they got stuff that makes it easy.
Making it look like anything with varying distance to a varying print surface is gonna be fun; but you can call it abstract art and just leave (multicolored?) blobs of ink behind you as you walk.
Combine it with wheeled heels and it could be a kids fad: streetwriter shoes! I bet Nike could sell millions.
source: I made the shoe :)
Impressive results indeed!
I'm still thinking of some way to lay down a line of "wildlife tracks" while walking. Like the illustrations in old books. This could work but it's not subtle.
I want people to look at each other and ask "when did a duck come through here?"
edit: you've advanced technology in an important way here: It's the most efficient possible arrangement for kicking the printer when it goes wrong. You should patent that. "method of minimizing latency of percussive printer maintenance"
