Stanford researchers are working on an application that uses eye tracking to enter passwords:
EyePassword allows gaze-based password/pin entry. It prevents shoulder surfing and does not generate any keyboard and mouse events making it more difficult to use standard event loggers. EyeSaver turns on the screen saver when a user looks away from the screen and automatically turns off the screensaver when the user looks back at the screen.
The software also has other applications like scrolling up/down, pointing and selecting things or switching to other programs.
Seems pretty interesting but I wonder how accurate it will be.