The city of Essen has been monitoring a part of its rockfall protection fences with the help of sensors as part of a pilot project since 2022. Therefore the system GUARD is used, which registers impacts and rope forces as well as recording other environmental data. In the past, this has made it possible to recognise falling rocks and trees and initiate a targeted inspection of the structures. The rope forces are used to draw conclusions about the fill level of the structure. Continuous monitoring by the installed sensor technology can make the inspection of the structure more efficient and reduce the inspection effort. The presentation presents the experience gained from the planning, installation and operation of the system and discusses the potential of sensor-based monitoring for the structural monitoring of geotechnical protective structures.