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.
It does emit ink! It uses a modified hand-held inkjet printer (princubestore.com). The distance to the print-surface is fixed by tiny wheels which make direct contact. For some reason the article doesn't include a video of it working, if you'd like to see it in action: https://www.instagram.com/p/CwN3NFBv4sO/
Thank you for the clarification; from the article it looks like a piece of costume art.
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"