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We report on our extended research on GymSkill, a smartphone system for comprehensive physical exercising support, from sensor data logging, activity recognition to on-top skill assessment, using the phone's built-in sensors. In two iterations, we used principal component breakdown analysis (PCBA) and criteria-based scores for individualized and(More)
We present GymSkill, a personal trainer for ubiquitous monitoring and assessment of physical activity using standard fitness equipment. The system records and analyzes exercises using the sensors of a personal smartphone attached to the gym equipment. Novel fine-grained activity recognition techniques based on pyramidal Principal Component Breakdown(More)
Vision-based approaches for mobile indoor localization do not rely on the infrastructure and are therefore scalable and cheap. The particular requirements to a navigation user interface for a vision-based system, however, have not been investigated so far. Such mobile interfaces should adapt to localization accuracy, which strongly relies on distinctive(More)
Self-reporting techniques, such as data logging or a diary, are frequently used in long-term studies, but prone to subjects' forgetfulness and other sources of inaccuracy. We conducted a six-week self-reporting study on smartphone usage in order to investigate the accuracy of self-reported information, and used logged data as ground truth to compare the(More)
Digital market places (e.g. Apple App Store, Google Play) have become the dominant platforms for the distribution of software for mobile phones. Thereby, developers can reach millions of users. However, neither of these market places today has mechanisms in place to enforce security critical updates of distributed apps. This paper investigates this problem(More)
In this paper, we review the use of gameful design in the automotive domain. Outside of vehicles the automotive industry is mainly using gameful design for marketing and brand forming. For in-vehicle applications and for applications directly connected to real vehicles, the main usage scenarios of gameful design are navigation, eco-driving and driving(More)
With physical mobile interaction techniques, digital devices can make use of real-world objects in order to interact with them. In this paper, we evaluate and compare state-of-the-art interaction methods in an extensive survey with 149 participants and in a lab study with 16 participants regarding efficiency, utility and usability. Besides radio(More)
Vision-based approaches are a promising method for indoor navigation, but prototyping and evaluating them poses several challenges. These include the effort of realizing the localiza-tion component, difficulties in simulating real-world behavior and the interaction between vision-based localization and the user interface. In this paper, we report on initial(More)
People feel very comfortable when they interact with their mobile devices by using natural user interfaces (NUIs). However , when they enter a vehicle, this feeling degrades rapidly, since many in-vehicle infotainment systems (IVIs) still do not offer natural user interfaces and use different user interface interaction paradigms. For this reason, we show(More)