peer-reviewed This thesis explores the implications of embedding sensing technologies in artefacts in public spaces, and examines how people come to understand and interact with them. Sensing and display technologies will increasingly be embedded into the physical objects and surfaces of our everyday world, due to miniaturization and falling costs. Sensing-based interactions are already being used in the common everyday appliances in our public places, e.g., to control lights, taps, toilets and doors by exploiting body movement. However, the effect of replacing a physical control with a sensing-based control is not only to severely reduce the sense of control in the interaction but in effect it creates an ‘invisible’ interface. This can not only make it difficult for identification, but removes the physical object/interface that can channel users’ intentions and expressions that could be leveraged to provide system feedback. Another challenge in using sensing-based interactions in public settings is that they require special considerations such as immediate usability, short-duration interaction, and shared use. In this thesis, the issue of legibility is developed, explored, and evaluated through a variety of experimental probes and prototypes. The contextual implications of these systems are then explored in different public settings. The prototypes elaborated in this work were developed using a rapid prototyping approach. This approach builds on a custom middleware platform that allows us to evaluate the designs in different settings, and goes beyond once-off or proof-of-concept lab demonstrators. We examine factors such as use and appropriation of these prototypes outside the lab, in real-world demonstration situations in order to evaluate whether our designs were successful in making the prototype legible enough for users to interpret the system, both its activity and their relation to it. The findings reveal a number of important considerations in how we should design for technologies that transform the spaces they occupy. In particular they indicate that if people are to be aware of anything then it has to be explicitly made publicly available to their perceptions within the space they occupy.