A Canadian company has developed a technology called Eyebox2 that it says can monitor the gaze of passersby and respond to shifts in attention,  even tracking multiple people at once,  and even from more than 30 feet away.

The company says the advertising potential is large, wherein outdoor or unconventional ad space could be sold "by the eyeball." In addition, the technology could provide a new kind of test lab for evaluating and refining ads in unusual contexts.