In this paper, we explicate our research on technology-mediated urban experience specific to two hyper-local tests in which the space of the 'public' is transformed into a virtual network by connective broadcasting. The first case study presents collective mapping in Rio de Janeiro toward increased civic engagement and sustainability, the second tests documentation of political demonstrations for strategic and archival purposes for Occupy Boston. Grouped under the term "participatory urbanism," the projects intend to explore how an individual activates interstitial space (between the physical city and hovering networks, between public and private) by engaging technology and civic media to affect change in the built environment. The physical and virtual environments serve as reciprocal sources of information, engendering a collective practice of shared encounters. We investigate how such encounters of user-centered activity through mobile and web-based media support or implicate the perception and manipulation of the built environment over spans of time and locations, and will highlight qualitative elements of a mobile and web platform designed for successful civic engagement and participatory urbanism.