I had Google Glass when it came out. It was essentially this, but the tech at the time was still too bulky and voice and other things that would've made it better were not quite ready yet. A little too ahead of its time, but the idea was there. In fact, since then, I've seen attempts to do what you're asking, and we're getting closer. The problems now are the cameras & microphones and privacy, and bulkiness of the devices.