When I was growing up my dad always wore a wrist watch. On the few occasions he ever took it off, it looked like he was still wearing something around his wrist due to the absense of the massive tan he got from working outside.
I think a wrist phone is a great idea, but wouldn't buy one unless it could actually function as a phone. I personally hate wrist watches, but would start to like them if I could remove the phone from my pocket, and I'm sure a lot of others would too.
A. Full Android watches with SIMs and everything have existed for years. If that's what you want why don't you have one already?
B. The whole point is to be able to to have a personal area network with a single control unit managing the experience across all of your contacted devices, not a series of independent devices each vying for your attention in a disjointed way. Think of the watch as an extension of your existing phone that you can access without having to pull the phone out of your pocket, enter your pin, find your app, and finally do an action. This also allows the watch to offload the heavy processing tasks to the powerful device you already have in your pocket 99% of the time. What good is having your phone, and a second, less powerful processor in your watch both running 100% of the operations in parallel?