Portable smart devices are getting more and more popular. Many people prefer smart solutions over old devices or pen-and-paper. But developing applications for mobile devices is a challenging task. First, it is difficult to create an intuitive, easy to use interface; second as current mobile platforms are not compatible, the application must be rewritten on all of them. Furthermore it is not trivial to design multimodal interfaces (including speech and graphical I/O) which really improve software usability. For these reasons our goal is to create an XML based scalable, cross platform, multimodal user interface description format and the corresponding interpreter software for different platforms. This technology makes development for mobile devices much faster and easier.