An Israeli company called ID-U Biometrics thinks that the patterns of eyeball movement are unique to each individual, and are therefore a definitive means of identifying people:
In ID-U Biometrics’ system, the user has to watch a moving object onscreen, while the camera observes the motion of their eyes. Since the way our eyes move is based on a combination of factors –such as anatomy, physiology, behavioral characteristics, eye structure–it’s a signature that simply can’t be duplicated or forged, according to its developers.[…]
Continue reading… “Eyeball Movement as a Means of Identifying People”