One shortcoming of self-describing smart objects augmented with digital resources is the limitation of output modalities due to their long established physical appearances. To overcome this drawback intangible representations e.g., sound, video projection etc. are usually coupled with the tangible representations of smart objects that enable access and interaction with their value added features. In this paper, we explore two mobile interaction techniques that associate such intangible representation to smart objects using a pico projector augmented camera phone. The first technique utilizes a Magic Lens metaphor applying mobile augmented reality (contextual information is overlaid while looking at a smart object through camera) to uncover and interact with smart objects. The second technique, Personal Projection follows similar mechanisms in discovery and interaction, except information is projected onto the nearest surface. We report the implementation of these two techniques and a comparative qualitative study with three prototype smart object applications. The findings give us deeper insights on the positive and negative aspects of these two techniques and open up a range of stimulating research issues that we discuss in the paper.

The RELATE interaction model is designed to support spontaneous interaction of mobile users with devices and services in their environment. The model is based on spatial references that capture the spatial relationship of a user's device with other co-located devices. Spatial references are obtained by relative position sensing and integrated in the mobile user interface to spatially visualize the arrangement of discovered devices, and to provide direct access for interaction across devices. In this paper we discuss two prototype systems demonstrating the utility of the model in collaborative and mobile settings, and present a study on usability of spatial list and map representations for device selection.