The accurate measurement of wind turbine tower motion is crucial for assessing structural integrity, identifying damages, and estimating remaining useful life. In this study, the development of a smart sensor system is presented, which combines acceleration measurements, real-time kinematic measurements, and SCADA data to accurately determine the motion of slender structures. The proposed setup offers a cost-effective and easily deployable solution. Installed on the top of the wind turbine nacelle, the sensor system collects data to calculate the tower motion. Real-time kinematics measurements serve as correction input for a state estimator, to enhance accuracy and reliability. Data gathering and processing occur directly on the sensor node, allowing for efficient transfer. Test measurements on a wind turbine tower have demonstrated the effectiveness of the system for accurate motion measurements. Beyond wind turbine manufacturing, this sensor system holds potential for application in several domains, including tall buildings and bridges, where the detection of vibrational movements is valuable for structural health monitoring.