This chapter discusses some of the challenges museums and galleries face when designing handheld technologies with learning purposes, such as museum guides. It describes practicalities in the development and deployment of multimedia guides through the case study of mi-Guide, as well as other examples of handheld devices. Multimedia guides provide access to a much richer experience, opening up collections to a far greater extent than is possible within the confines of a physical space and enhancing the museum's educational potential. Research carried out by Fusion Research and Analytics members of the American Alliance of Museums (US) and the Museums Association (UK) identified several important trends and developments which will influence significantly the development of handheld museum guides. The European funded Learning Museum Network Project (LEM) has also identified important trends and developments, noting that museum visitors using the Internet are now of the same relevance to museums as physical visitors.