Polemics about base stations of cellular telephones have become a recurrent source of conflict among telecommunication companies, city authorities and citizens. Following early work performed within the framework of a doctoral thesis, the french research projet ANR Samper (2008-2011) has set up, for the first time, a network of monitoring stations in an urban environment, whose measurements are processed continuously by geostatistical methods, in order to inform daily the inhabitants on the hourly variations of radioelectric exposure in their surroundings. More precisely, the system uses a kriging of the exposure measurements including as external drift the output of a physical model of the propagation of the radioelectric signal emitted at different frequencies by the base stations. We present the implementation of the ANR Samper pre-operational monitoring system set up during several months in a section of the city of Grenoble.