Hate to rain on this guy's parade, but conductive ink pens have already been for sale for quite some time. If he wants to reinvent the wheel, enjoy. Quite honestly, this looks amateuristic, so gefundenes Fressen for artists and "installations", I guess. Sorry for being so negative, it just feels unfair sometimes that hardware designers working their ass of to get you all these nice fancy iGadgets are rarely held in high esteem, while "artists" can "invent" something old, build something trivial (20 lights in parallel!) and makea big deal out of it.
The conductive ink plotter which was featured here some time ago is something completely different, of course.