Acontextuality of the mobile phone often leads to a caller’s uncertainty over a callee’s current state, which in turn often hampers mobile collaboration. We are interested in re-designing a Smartphone’s contact book to provide cues of the current situations of others. ContextContacts presents several meaningful, automatically communicated situation cues of trusted others. Its interaction design follows social psychological findings on how people make social attributions based on impoverished cues, on how self-disclosure of cues is progressively and interactionally managed, and on how mobility affects interaction through cues. We argue how our design choices support mobile communication decisions and group coordinations by promoting awareness. As a result, the design is very minimal and integrated, in an “unremarkable” manner, to previously learned usage patterns with the phone. First laboratory and field evaluations indicate important boundary conditions for and promising av...