I'm excited for these type of wearables as input devices for head-mounted HUDs/AR. Google Glass currently uses voice recognition and a capacitive strip, which is fine, as Glass is only for briefly looking up information. As AR develops, it will need more complex input methods, and I see these as some vague possibilities:

* Hand/wrist/arm mounted input (Nod, Myo, watches, chorded keyboards, etc...)

* Eye-tracking (technology exists, but needs to be miniaturized and developed further to fit within a glasses frame)

* Head movement (tiling your head, winking, etc.)

* Computer Vision (ie. AR develops enough to use your hand in front of you to intuitively interact)