  Gaze tracking is a useful human-to-computer interface, which plays an
increasingly important role in a range of mobile applications. Gaze calibration
is an indispensable component of gaze tracking, which transforms the eye
coordinates to the screen coordinates. The existing approaches of gaze tracking
either have limited accuracy or require the user's cooperation in calibration
and in turn hurt the quality of experience. We in this paper propose vGaze,
continuous gaze tracking with implicit saliency-aware calibration on mobile
devices. The design of vGaze stems from our insight on the temporal and spatial
dependent relation between the visual saliency and the user's gaze. vGaze is
implemented as a light-weight software that identifies video frames with
"useful" saliency information, sensing the user's head movement, performs
opportunistic calibration using only those "useful" frames, and leverages
historical information for accelerating saliency detection. We implement vGaze
on a commercial mobile device and evaluate its performance in various
scenarios. The results show that vGaze can work at real time with video
playback applications. The average error of gaze tracking is 1.51 cm (2.884
degree) which decreases to 0.99 cm (1.891 degree) with historical information
and 0.57 cm (1.089 degree) with an indicator.
