Mobile phones have become full-featured mobile computers. Applications providing good user experience and taking full advantage of the increasing capabilities of mobile phones are still rare. One such application is audio and video on mobile phones which is expected to become a killer application in the near future. A lot of valuable audio and video content is hidden in archives of content providers. We are developing an application that enables a user to perform content-based search for audio and video content in large databases and play it on a mobile phone virtually anywhere, at any time. Our approach to application development focuses on the adoption of agile software development methodologies and user-centered design, emphasizing iterative user-interface development involving usability engineers and non-technical users. Thus, the application evolves according to the needs of the end user, providing maximized usability and customer satisfaction.