The rates of job injuries and fatalities in construction sites are still too high, with respect to other industrial working places. Statistics show that there are a few main types of risk accidents causing the higher number of fatalities. This paper suggests the development of a novel low intrusive real-time monitoring system in support of health and safety management in construction sites and addresses its basic application cases. It is mainly intended as a support system for those inspectors in charge of the correct application of the measures dictated by the Health and Safety Plan. Its application in construction sites is rendered convenient by its low intrusiveness and easy expandability with the real work progress. Finally, first successful field tests carried out in a large construction site, regarding several residential block of flats under construction in an Italian town, are presented.