Inhaltsangabe:Abstract: The market of mobile technologies is growing at an enormous rate worldwide. With the latest developments in technology, new services are being invented which were not even possible some years ago. As new devices, applications and services emerge, also the number of mobile users is increasing in a rapid manner. Mobile broadband networks like UMTS, EDGE or Wireless LAN make it possible to reach a large group of users who gain access with their personal mobile devices, equipped with multimedia and data capabilities. Due to this development, new interesting possibilities arise for many areas. One of these areas is the tourism sector, which is being referred to in this thesis. The so-called m-tourism (mobile tourism) is an emerging field with an enormous marketing potential, as described in Chapter 2. Recent hardware inventions and developments are greatly pushing the market share. Companies are offering tailored products filling the needs of their customers. Personalization of services becomes a popular trend in this sector. But what do users think about such a mobile tourism service? Do they feel the service has added benefits, compared to traditional media and Web-based services? Are those products really user friendly? What would be the crucial applications and qualities that make the big difference ? A range of usability issues concerning mobile services is being discussed in the science community; are there already viable, good solutions? With the recent hype of so-called location based services, the consumer keeps calling for more usable products, featuring more intuitive interfaces. Others may fear being overwhelmed with features. Especially for the senior users, a relatively big target group for most mobile applications, these products often remain a mystery. Usability has been and should always remain a key element for quality software and successful applications. In this thesis, several applications are described, some of their user interfaces are analyzed and major flaws discovered. Furthermore, a corresponding prototype user interface is introduced with a specific analysis of each development step, taken from the book The Usability Engineering Lifecycle by Deborah J. Mayhew. Once prototypical realisations are available, users can validate the implemented approaches and evaluate concepts and realization details from their point of view. Such first user experiences are a valuable guidance for further [...]