This paper discusses ETAG, a formal model for design representation, and ETAG-based design as a method for user interface design. The paper starts with an introduction of ETAG as a design representation. This is followed by a description of ETAG-based design and using the notation to represent relevant aspects of the work context. Next, we discuss the differences between computer software design and media product design, concluding that media design is a much more flexible, iterative process and prototyping-based process in which adaptation of the design of mobile applications extends into the maintenance phase. To cover further developments towards focusing on user needs and wishes by means of co-design practices, and to cover for ubiquitous computing and interaction with sensors and interactive environments, we propose to use sensory labs and to create living labs to move the usability lab into the real world.