Very cool idea. Yeah real holographic projection is still a ways off, especially from a portable emitter. AR however is much closer. There’s an increasing focus on AR tech and making it smaller and cheaper- I saw a glasses the other day for $400 that projects a real 1080p screen onto your field of view and can talk to a phone. That stuff will only get better. The key is making it lightweight, have a long battery life, and fashionable. You also need some kind of separate input device, if you assume the phone remains in the pocket as a compute module. Or for those willing to accept a larger watch, perhaps the watch becomes the phone rather than an accessory to one. There’s of course issues of size, weight, battery life, etc; but as tech improves those will get better. And in theory, the main reason you don’t have the watch as the main phone is lack of screen size; if an external AR display was common that problem goes away.