Yeah, I'd think it is really a non-starter. I've been playing for 30 years, and can't imagine using something like that; reason being that I had reconstructive surgery on my left wrist about 15 years ago, and having had my hand in plaster for 3 months while the ligaments healed led me to a lengthy period where my hand 'wasn't mine', making it very difficult to play. And that was with a hand which was in truth functioning fully, just stiff and in need of physio. Without the feedback that you get from a real digit, I can't see it working other than as a makeshift slide to play with.
Not to say that it won't happen in the future, but I don't think this is it.
In terms of practicality otherwise, the exposed actuating wire looks like it would cause trouble (getting caught in places etc).