In this paper, we report on a user-centered, iterative design process for augmenting sports equipment with ubiquitous computing technology. In several design iterations, a fully working system for training and physiotherapy has been developed and deployed using hard- and software components of ubiquitous computing technology. We report on the design and development process that led to this system. Based on our experience we generalize the specific processes to general ubicomp systems. The validity of our approach has been verified by a larger user study.