Easy takings for street robbers
Unless there's going to be a dorky looking headband option, it will be so easy for robbers to run past and snatch them off people's faces.
With that in mind, such technology might be better suited to professional environments where no one nearby is likely to be a thief.
An IR and UV display mode will be most useful to a few professions I can think of, and even more if it has a 12MP camera and LCD with zoom mode.
I think a bluetooth remote control would be most useful - something small that you wear like a fingerless glove or an inward facing ring worn on your index finger and controlled with your thumb. Could be quicker to use than awkward voice or head movements. (Remember where you heard this first!)