Vision-based user interfaces are a feasible and advantageous modality for wearable computers. To substantiate this claim, we present a robust real-time hand gesture recognition system that is capable of being the sole input provider for a demonstration application. It achieves usability and interactivity even when both the head-worn camera and the object of interest are in motion. We describe a set of general gesture-based interaction styles and explore their characteristics in terms of task suitability and the computer vision algorithms required for their recognition. Preliminary evaluation of our prototype system leads to the conclusion that vision-based interfaces have achieved the maturity necessary to help overcome some limitations of more traditional mobile user interfaces.