We fitted keyboard onto our screens, AR devices normally come with a joystick or something.
I have high hopes for similar projects to Tap Keyboard or the Myo armband, that continue to evolve on something that IMO has large implications on how we can evolve as a society the same way smartphones did. A wearable input device that was _good_ (defined by not being cumbersome, probably even fashionable and functional, as should match current input) would be for me the extra step .
There have also been various alternate input styles for phones but nothing's ever taken off.
I mean, if you could use a pen and paper to interface with a computer, you're standing on the shoulders of centuries of experience about how to produce a nice pen-paper experience, at a really cheap price. A newcomer in the world of interface hardware has to overcome the fact that everybody finds a new interface horrible for years, aside from the crazy technical and industrial challenges of producing something at a price/performance ratio that's better than entrenched technologies.