The new multimodal reality provides the mobile user with a rich variety of methods for interfacing with a system, including speech, gestures and movements, touch, typing, and more. Therefore, designing multimodal interactions requires the integration of multiple recognition technologies, sophisticated user interfaces, and distinct tools for input and output of data. Join us in a discussion of the technological and usability challenges inherent in multimodality- based UI, the technologies and design which are innovative, and usability challenges inherent in multimodality- based user interfaces.