This paper outlines an m-learning solution, "Global MedAid", which aims to provide learning resources and tools for personnel in various roles in disaster or emergency situations. It outlines the development process and presents the design considerations and solutions for developing a cross-platform application combining a wide range of media types for on-line and off-line use, depending on whether or not there is access to a data signal. The design process took into account current mobile health and related applications, addressing the ways in which both educational resources and performance support tools could be combined and accessed in the field. The paper also shows how partners and users have been involved in the design process and in the evolution of the app. The resulting Proof of Concept has been evaluated with over a hundred users across 21 countries, and initial findings show that users thought it was both useful and effective.