In order to support interactive high-fidelity prototyping of postWIMP user interactions, we propose a multi-fidelity design method based on a unifying component-based model and supported by an advanced tool suite, the OpenInterface Platform Workbench. Our approach strives for supporting a collaborative (programmer-designer) and user-centered design activity. The workbench architecture allows exploration of novel interaction techniques through seamless integration and adaptation of heterogeneous components, high-fidelity rapid prototyping, runtime evaluation and fine-tuning of designed systems. This paper illustrates through the iterative construction of a running example how OpenInterface allows the leverage of existing resources and fosters the creation of non-conventional interaction techniques. Categories and Subject Descriptors H5.2 [Information interfaces and presentation]: User Interfaces.