Between Wearable and Spatial Computing: Exploring Four Interaction Techniques at the Intersection of Smartwatches and Head-mounted Displays

In this paper we introduce four bi-directional interaction techniques that sit between smartwatches and head-mounted displays (HMDs): gaze dwell, gaze and tap, mid-air touch, and trackpad. Our goal is to expand the input and output space of smartwatches while leveraging this as a familiar anchor for digital content that also provides HMDs with an inconspicuous and available input space. In an initial study (N=12) we characterize user performance, experience, and preference with the techniques in a task involving discrete and list-based selections, where interface targets were anchored to participants' wrists and heads. While our findings show that all four techniques were usable and effective, mid-air touch and gaze and tap were the best-performing and favored techniques by most participants – who described them as "precise", "fast", or "intuitive". We conclude by describing potential future work in this domain of cross-device interaction.