  The movement of a user's face, easily detected by a smartphone's front
camera, is an underexploited input modality for mobile interactions. We
introduce three sets of face-engaged interaction techniques for augmenting the
traditional mobile inputs, which leverages the combination of the head
movements with touch gestures and device motions, all sensed via the phone's
built-in sensors. We systematically present the space of design considerations
for mobile interactions using one or more of the three input modalities (i.e.,
touch, motion, and head). The additional affordances of the proposed techniques
expand the mobile interaction vocabulary, and can facilitate unique usage
scenarios such as one-hand or touch-free interaction. An initial evaluation was
conducted and users had positive reactions to the new techniques, indicating
the promise of an intuitive and convenient user experience.
