This thesis investigates challenges and requirements related to both domain area and usability principles through investigating task-support for incident commanders in the police. To this end, domain knowledge has been collected through field studies, interviews and observation, and a prototype combining these requirements with state of the art mobile technology has been developed. The prototype has been developed to support tasks related to resource allocations. It combines the use of a map-based interface with icons with lists and forms, and uses direct manipulation as a part of the interaction. Evaluations have been conducted with both usability and domain experts, and results from the evaluations are categorized, discussed and finally used to put forward design implications. The findings of this thesis include a set of design implications deduced from (1) careful investigation of the domain area, (2) usability theories and design guidelines, and (3) evaluations of a developed prototype. The study has proven that the uniqueness and characteristics of emergency situations does not allow us to rely on design theory alone, and a combination of usability and domain expert is essential. The results from the evaluations and the design implication put forward show that the work in this field is highly feasible, yet more knowledge about the domain area is required to further facilitate for added value when solving tasks. Results also confirm that state of the art mobile devices are well-suited for decision-support within emergency response. Furthermore, the challenges, requirements and alternative solutions presented in this thesis are highly transferrable to other emergency agencies.