Sensor networks have appeared on the 'radar' of metrology only recently and a rigorous treatment and metrological assessment have not yet been established. However, sensor networks as measuring systems underpin many developments in digital transformation, with applications ranging from regulated utility networks to low-cost Internet of Things (IoT). The metrological assessment of sensor networks necessitates a fundamental revision of calibration, uncertainty propagation and performance assessment and new approaches for information and data handling regarding the individual sensors and their interactions in the network to allow a systems metrology approach to be established. This contribution introduces some initial findings from recent research and gives an outlook into future developments.