The authors discuss their experience with a number of mobile telephony projects carried out in the context of the European Union Information Society Technologies research program, which aims to develop mobile information services. They identify areas where use of smart phones can enable pervasive computing and offer practical advice in terms of lessons learned. To this end, they first look at the mobile telephone as * the end point of a mobile information service,* the control device for ubiquitous systems management and configuration,* the networking hub for personal and body area networks, and* identification tokens.They conclude with a discussion of business and practical issues that play a significant role in deploying research systems in realistic situations.