Recent efforts in the field of mobile computing are directed toward speech-enabling portable computers. This paper presents a method of multimodal interaction and an application which integrates speech and pen on mobile computers. The application is designed for documenting traffic accident diagrams by police. The novelty of this application is due to a) its method of fusing the speech and pen inputs, and b) its fully embedded speech engine. Preliminary experiments showed flexibility, versatility and increased naturalness and user satisfaction during multimodal interaction.