Lack of regular physical activity and high stress levels are the leading causes of several illnesses. There is thus a real need for a personal low-cost and mobile monitoring solution over extended periods to prevent health risks. Based on the above fact, this article presents a system capable of estimating and monitoring both stress and fitness levels without a physical consultation of a medical specialist. The system consists of three main subcomponents: a mobile real-time acquisition of physiological as well as subjective data, an expert model for stress and fitness estimations based on physiological signals collected from wireless vital sensors, and a secure and scalable telematics platform on which the entire system is embedded. Features and tasks performed by the telematics platform will be presented. The experimental part of the work involved a representative number of subjects. Results for 110 subjects whose fitness levels were assessed at different periods of the year and 50 individuals whose stress scores were assessed at different times of the day showed a high correlation of the estimated values with the true ones. The application of such a low-cost monitoring system will improve the quality of service in preventive medicine.