The form factors of current wearable devices are designed and limited to be worn at specifically defined on-body locations (such as the wrist), which can limit the interaction capabilities based on physical constraints in body movement and positioning. We investigate the design of a multi-functional wearable input device that can be worn at various locations on the body and may as well get mounted onto objects in the environment. This allows users to adjust the device's location to different affordances of varying situations and use cases. We present a SnapBand as such a multi-location touch input device that can be quickly snapped to different locations.

We present Movelet, a self-actuated bracelet that can move along the user's forearm to convey feedback via its movement and positioning. In contrast to other eyes-free modalities such as vibro-tactile feedback, that only works momentarily, Movelet is able to provide sustained feedback via its spatial position on the forearm, in addition to momentary feedback by movement. This allows to continuously inform the user about the changing state of information utilizing their haptic perception. In a user study using the Movelet prototype, we found that users can blindly estimate the device's position on the forearm with an average deviation of 1.20cm to the actual position and estimate the length of a movemement with an average deviation of 1.44cm. This shows the applicability of position-based feedback using haptic perception.

We present a gaze-based interaction approach that maps a single rotary control knob to multiple interfaces in the car using the user's gaze to determine the respective interaction context. By this, the complexity of physical interfaces (e.g. number of buttons) can be reduced and abstracted to a single remaining physical control interface located at the steering wheel to allow for interaction that doesn't require drivers to take their hands off the steering wheel. We implemented a prototype that uses multiple eye-trackers in a driving simulator to explore the concept of gaze mapping.

We present FaceTouch, a novel interaction concept for mobile Virtual Reality (VR) head-mounted displays (HMDs) that leverages the backside as a touch-sensitive surface. With FaceTouch, the user can point at and select virtual content inside their field-of-view by touching the corresponding location at the backside of the HMD utilizing their sense of proprioception. This allows for rich interaction (e.g. gestures) in mobile and nomadic scenarios without having to carry additional accessories (e.g. a gamepad). We built a prototype of FaceTouch and conducted two user studies. In the first study we measured the precision of FaceTouch in a display-fixed target selection task using three different selection techniques showing a low error rate of 2% indicate the viability for everyday usage. To asses the impact of different mounting positions on the user performance we conducted a second study. We compared three mounting positions of the touchpad (face, hand and side) showing that mounting the touchpad at the back of the HMD resulted in a significantly lower error rate, lower selection time and higher usability. Finally, we present interaction techniques and three example applications that explore the FaceTouch design space.

Belt is a novel unobtrusive input device for wearable displays that incorporates a touch surface encircling the user's hip. The wide input space is leveraged for a horizontal spatial mapping of quickly accessible information and applications. We discuss social implications and interaction capabilities for unobtrusive touch input and present our hardware implementation and a set of applications that benefit from the quick access time. In a qualitative user study with 14 participants we found out that for short interactions (2-4 seconds), most of the surface area is considered as appropriate input space, while for longer interactions (up to 10 seconds), the front areas above the trouser pockets are preferred.

This paper presents Glass Unlock, a novel concept using smart glasses for smartphone unlocking, which is theoretically secure against smudge attacks, shoulder-surfing, and camera attacks. By introducing an additional temporary secret like the layout of digits that is only shown on the private near-eye display, attackers cannot make sense of the observed input on the almost empty phone screen. We report a user study with three alternative input methods and compare them to current state-of-the-art systems. Our findings show that Glass Unlock only moderately increases authentication times and that users favor the input method yielding the slowest input times as it avoids focus switches between displays.

To maintain a mobile form factor, the screen real estate of a mobile device canIn this paper we present SurfacePhone; a novel configuration of a projector phone which aligns the projector to project onto a physical surface to allow tabletop-like interaction in a mobile setup. The projection is created behind the upright standing phone and is touch and gesture-enabled. Multiple projections can be merged to create shared spaces for multi-user collaboration. We investigate this new setup, starting with the concept that we evaluated with a concept prototype. Furthermore we present our technical prototype, a mobile phone case with integrated projector that allows for the aforementioned interaction. We discuss its technical requirements and evaluate the accuracy of interaction in a second user study. We conclude with lessons learned and design guidelines.

The vision of pervasive ambient information displays which show relevant information has not yet come true. One of the main reasons is the limited number of available displays in the environment which is a fundamental requirement of the original vision. We introduce the concept of an Ambient Mobile Pervasive Display AMP-D which is a wearable projector system that constantly projects an ambient information display in front of the user. The floor display provides serendipitous access to public and personal information. The display is combined with a projected display on the user's hand, forming a continuous interaction space that is controlled by hand gestures. The paper introduces this novel device concept, discusses its interaction design, and explores its advantages through various implemented application examples. Furthermore, we present the AMP-D prototype which illustrates the involved challenges concerning hardware, sensing, and visualization.

Loupe is a novel interactive device with a near-eye virtual display similar to head-up display glasses that retains a handheld form factor. We present our hardware implementation and discuss our user interface that leverages Loupe's unique combination of properties. In particular, we present our input capabilities, spatial metaphor, opportunities for using the round aspect of Loupe, and our use of focal depth. We demonstrate how those capabilities come together in an example application designed to allow quick access to information feeds.