We investigate how smart phones can augment site-specific services - that is, electronic services or applications that reside in a specific location. Site-specific services already exist in the form of ticket machines, electronic information kiosks, interactive product catalogues, and so on. However, integrating users' smart phones into these interactions can enhance service functionality while reducing deployment costs. Our approach offers several benefits. By using personal information stored on smart phones, site-specific services can automatically tailor their actions to suit a particular user. Our research led us to develop the Mobile Service Toolkit: a client-server software framework supporting the development of site-specific services that exploit interaction with smart phones. We discuss the Mobile Service Explorer (MST) and present case studies of two site-specific services implemented using it.