It's all being done backwards...
I just feel that 'Smartwatches' are actually a 'backwards' way of doing this. What I want is some personal network connected doo-dah (like a watch, or to get all 'Star Trek:TNG' - a badge) that'll be my own hotspot. It'll handle the network and it knows who I am so when another device is near it it works with it'll automatically configure that device with my own setup.
So, you have your 'watch' which is also the mobile network connected doo-dah. You pick up a tablet and the watch tells the tablet 'Hey - this is Fred. His email address is 'fred@hotmail.com' and, and he uses GDrive for cloud storage and these are all the account settings'. Then when I'm using the tablet everything is automatically setup for me. 'Handset' mobile phones will just become a pocket tablet as the watch doo-dah does the actual mobile networking stuff (if you have a hands-free headset you can talk without a 'phone' at all - or you can pretend to be a secret agent by talking directly into the watch).
And taking it further, you can use the doo-dah to walk into a '21st Century' version of a phone box (without the dodgy smells) and the doo-dah tells the phone box who you are and that you're a Skype, or Facetime, or Gtalk user and it sets itself up to access your details on that service. It could even have billing details.
And for businesses it'll make hotdesking far more flexible.
That's actually probably all not too far off - with mobile-wifi hotspots, NFC, bluetooth and cloud based services now. However, it would probably involve the co-operation of the big companies to work together on some sort of standard or else you'll just end up with the Google, Apple, MS watch which refuses to work with the other services.