I think it's a stupid idea. The "smart watch" technology is great for ALERTS and maybe simple push button replies and can integrate fine with a phone or tablet. But trying to use it as a "phone" or a "computer" is silly.
Voice-to-text input is an option and Siri/Cortana or whatever your flavor does a decent job but the function would be a battery hog.
Just let the watch be like an "extra" display and stop trying to make it in to a Dick Tracy watch/video-phone.