The wrist-worn computer is here but if you want to use it for person to person communications you'll struggle with data entry. Micro keyboards, canned responses and voice input don't add up to a usable input solution. If you don't want to pull out your smartphone every time you need to reply to a message (and surely that's the point) then you need to resolve this issue.
Well, not exactly. One company solved the problem twenty years ago. The company was Palm and the solution was Graffiti. A machine-readable, single stroke input solution that was so close to the standard alphabet that with only limited learning users could enter information into their pocket devices without having to look at them or fiddle with cumbersome keyboards.
Its ideal for use on a smart-watch because it works on a small screen, can be entered with a single finger and can even handle extended character sets. Not having to look at the screen whilst writing is another bonus of the technology.
Given that Palm sold off Graffiti when it split off Palm Source, there's a good chance that there's a technology owner just waiting to be procured for anyone who can afford to buy it.
Smart watches are going to be impossibly fiddly to use once they go mainstream. A simple input method is all that will be required to remove that problem.
That might just be Graffiti.