Chording keyboards are never likely to become mainstream because they have a steep learning curve. That doesn’t mean they aren’t a great idea or that they don’t work quite well. This looks like an unusually clever implementation of the concept.

The particular application makes a lot of sense. The combination of a wearable keyboard with extremely fast typing and text-to-speech would solve a real problem for people who can’t talk.

Personally, I’ve played around with chording, but came to the conclusion that I actually don’t need that much typing speed. Most of my typing is either coding or writing emails. In either case, I stop to think about what I want to write often enough to keep my maximum word rate quite low. I can type around 90 wpm on a regular keyboard, which is still faster than I can compose.