Except that people want some kind of textile feedback for what they type—which is why SelfieType likely would only be just a “cool technology”
People want to type, and they want to do it quickly. Tactile feedback is nice... but most people do not engage in typing for the fun of it. The primary concerns for this are input reliability, ease & speed of setup, and learning curve.
You aren't using such a thing to replace your desktop keyboard. You're using it to replace your smartphone keyboard, and probably primarily for typing emails without having to carry things around
Swipe-style input on phones seems more popular than keypresses, despite having lower input reliability, more difficult setup, and an inability to enter certain words.
It's faster than typing, though, as long as the word you want to enter is part of the swipe input method's dictionary.
I can't trust emails on a smartphones because they're so error-prone. If this thing is reliable in its input, and easy to setup, then the "unpleasantness" of typing on a desk is very low on the list of concerns, unless it's extremely unpleasant, if not outright painful.
And unless you're a hunt-and-pecker (which couldn't feasibly use the tool in the first place, afaict), I don't see how it could be that unpleasant. And playing with the idea on my desk.. it's not the greatest feeling, but its hardly a showstopper.
It's not a general keyboard replacement. It's a few-usecase and higher-constraint keyboard replacement; the only thing that matters is whether it supports those specific fewer usecases significantly better than the currently available alternatives, because it doesn't hinder using the general tool as a fallback.
Tactile feedback + no need to mess around with bluetooth configurations (or to even support bluetooth). Actually this could be used to revive dead keyboards...