We present a novel approach for prototyping, testing and evaluating multimodal interfaces, OpenWizard. OpenWizard allows the designer and the developer to rapidly evaluate a non-fully functional multimodal prototype by replacing one modality or a composition of modalities that are not yet available by wizard of oz techniques. OpenWizard is based on a conceptual component-based approach for rapidly developing multimodal interfaces, an approach first implemented in the ICARE software tool and more recently in the OpenInterface tool. We present a set of wizard of oz components that are implemented in OpenInterface. While some wizard of oz (WoZ) components are generic to be reused for different multimodal applications, our approach allows the integration of tailored WoZ components. We illustrate OpenWizard using a multimodal map navigator.