I think it would be easy to build a very high end computer in a notebook style that can sit in a case that straps on like a back pack or side pack and uses a HUD shield that's like a very large pair of glasses, but the power to run it for more than just a few minutes will be a killer. Yes we now have notebook batteries that last for several hours of use, but the existing HUD technology really draws a lot of power, much more than the notebooks do. Thus the power source would have to be about ten times what is now used for a notebook - that's a lot of space and a lot of weight. Then you have to add in the sensors etc for the gesture style input system and power for that.

I do seem to remember seeing an article on a virtual reality system a few years back that worked with a HUD and a special sensor suit to detect body movement and gestures to feedback to the computer. But the whole thing worked of the mains and fed through a large desktop computer, so it's likely you could get the computer down in size, but that power issues still needs resolution.