Interestingly, such UI (well done, but seen such before) challenges the whole size of the smartphone as we know it, akin to a gaming keypad [1] challenging a keyboard.
If you want to take it a step further you can look into something such as Azeron[1], I've ordered one myself. But prooduction time is quite long (3 months). So I haven't experienced it myself, ordered it because of RSI issues.
[1] https://en.wikipedia.org/wiki/Gaming_keypad