In this article we use the formative evaluation of a prototype ‘assembly’ of pervasive computing technologies to specify design implications for emergency virtual teamwork tools. The prototype assembly, called “Overview”, was implemented in collaboration with police, fire and medical emergency services as part of the real life event management during the Tall Ships’ Races 2007 in Denmark. We describe how the emergency teams used the technologies for collaboration between distributed colleagues, to produce shared situation awareness, to manage efforts and resources and respond to minor emergencies. Trust in technology is a key need virtual teams identify in their endeavours to dovetail innovative technologies into emergency work. We show how practices of working up trust are supported by the PalCom open architecture (which was used to build Overview), and delineate design guidelines to enable the productive integration of pervasive computing.