Today Tobii announced a set of connected glasses that iterates on their previous model by being less clunky and capturing a wider field of view. When paired up with a Windows machine, the Tobii Glasses 2 can track where you're looking for the sake of pilot and sports training, as well as product marketing research. Though those aren't exactly everyday use cases, the technology is cool enough that it's easy to imagine different situations where this could be useful.
Tobii's other products are sensor bars that face the user and track their gaze as a source of input for PCs. I played with them a bit at CES and though they're a little crazy to use at first, it's easy to see the technology applied to wearables. The Tobii Glasses 2 are packed with proprietary sensors to get extra-precise for its gaze tracking, but it would be great to see some kind of software solution applied to Google Glass for touchless gesturing while out and about.