The objective of this work was the proposal, design, construction, and validation of a mobile health (m-health) system for dietetic monitoring and assessment, called SapoFit. This application may be personalized to keep a daily Personal Health Record (PHR) of an individual’s food intake and daily exercise, and to share this with a social network. The initiative is a partnership with SAPO – Portugal Telecom. SapoFit uses Web Services architecture, a relatively new model for distributed computing and application integration. SapoFit runs on a range of mobile platforms, it has been implemented successfully in a range of mobile devices and has been evaluated by over 100 users. Most users strongly agree that SapoFit has an attractive design, the environment is user friendly and intuitive, and the navigation options are clear.