it does make sense, if you'd like your iOs device to behave as a (sort of) giant Touch Bar check Quadro out... (http://quadro.me)

Did you try Quadro (http://quadro.me) instead? You need an iOs device tho, Android support is not yet available

I would if I were into iPhones. I'm on Android. Thanks anyway.

This has exactly what you are looking for, including USB support: http://quadro.me

That is pretty cool. Sadly iOS and Windows only, whereas I'm running Android and Linux.

You don't need to create one yourself http://quadro.me

I see, but I prefer mine, plus I want to let all the people have the source code, I am not interested in closed source apps.

there's actually a sort of external Touch Bar in case you need one http://quadro.me

I want to know if the hardware/OS supports a future 'touch-bar keyboard' extending the functionality to external devices

because otherwise it's useless to me, and I think pretty much everyone I work with