Emergency medical services (EMS) provide pre-hospital medical care and represent an important part of the rescue chain. The paramedic and physician's work is characterized by regular day-to-day services as well as extraordinary mis-sions within mass casualty incidents (MCIs). For several reasons, accessing, recording and communicating operational data are important tasks in any scenario of urgent medical care. Supporting an immediate and careful execution with the help of mobile technologies is accompanied by various challenges. While the mere technological problems, e.g. steady network connectivity or sufficient battery service life, are on the way of being solved within the near future, questions of usability remain. In this paper, we propose a single device solution for information, documentation and communication needs and describe our approach to ensure usability both in daily routine as well as in exceptional circumstances.