Apparatus for monitoring a parameter associated with a structural component comprises a module (1) which is attachable to the structural component and which is associated with a sensor (2) for making measurements of said parameter. The module incorporates a power supply (7) for powering the apparatus; a memory (4) for storing data from the sensor, and a processor (3) to process measurement signals from the sensor (2) and to store data in said memory (4). A display (5) for displaying measurements made by the sensor (2) may also be provided. The processor may make use of an algorithm such as a rainflow counting algorithm to reduce data stored. For energy saving, the sensor (2) is only powered on as required to take a measurement. The sensor (3) is interfaced to the processor through a signal processing subsystem (6) consisting of an amplifier and A to D converter, and each is turned on and off as required to power the sensor (2) for measuring. A sensor such as a tilt-switch (8) may also be used to control powering of the sensor (2). A communication link allows downloading of data from the memory, and recharging of the battery (7). Alternatively, the memory (4) and battery (7) are incorporated in a unit which is removable from the apparatus so that the data in the memory can be processed elsewhere.