I believe I will need a armband to get functionality I really want with current technology. Currently a watch face is too small for me to get meaningful information. A 2.5 inch curved display that curves with my wrist/arm and fastened with a clasp or band. Integrated celluar bits to be free from my phone. One day battery life is good enough (match my current phone). This would let me replace my phone for almost all tasks. I could not only communicate (very possible with voice and current smart watches), but consume as well.
The current crop of smart watches and Apple's "Watch" are not good for consuming anything complex like a longer email, webpage, book, YouTube, etc. Payment processing is interesting, but for something I do only a couple of times a day not a core feature I want. Same goes for things like boarding passes and hotel keys; I don't do those things enough for it to matter. I also don't go shopping enough to care about iBeacons and extra information popping on my watch.
At this point I know for the most part what I want after having used: Casio calculator watch, Palm Pilot, Palm VII, an original iPAQ, BlackBerries from 2005 to 2009, Palm Treo, and since then Android devices. I'll probably pickup a smart watch of some kind in the next year once they get closer to what I want them to do. In a couple of years bezels, battery life, etc should have enough changes that they will do exactly what I want, but if not it will be an armband.