Structural components of aircraft, civil and marine structures are prone to deterioration and require complex and costly maintenance activities. In recent years, much effort has been put into shifting from a preventive maintenance model, based on statistically scheduled interventions, to a predictive one, based on monitoring the actual health of the structure. The development of DIMOSS® (DIsplacement MOnitoring using Strain Sensors) software fits this context. DIMOSS® is a structural monitoring software for reconstructing fundamental quantities to assess the health of a structure, displacements and stresses. The software relies on strain sensors and it is based on the inverse Finite Element Method (iFEM). The software integrates iFEM and all the tools needed to design and operate a monitoring system. This paper introduces the theoretical background and the design approach of DIMOSS®. Moreover, it presents two successful experimental applications of the software: the monitoring of a stiffened composite wing-shaped panel and the live monitoring of an aluminium beam through the realisation of a structural digital twin.