Using Smart-Phone is eye-busy and hand-busy. You can’t use it while doing other things. Using on the road is dangerous.
It is because Smart-Phone is a mere miniature of desktop computer interactions. Human use hand/finger to input and get information by eye. It doesn’t change human machine interactions fundamentally.
Apple’s Watch is another desktop too. Using it is eye-busy and hand-busy.
Head Mount display or wearable glasses such as Google glass, Microsoft Hololens looks to me yet another miniature of desktop interaction. Using them is eye-busy, though hands may be free. Eye is already busy to catch information from the rich world and to guide reaction against the world. Why do we over-load eye more? Virtual Reality belongs to this eye-busy staff.
I think it is worth pursuing an approach which take information from eye (gaze tracker) without any interference in sight, take advantage of eye to react against world without any interference in sight again.