Abstract: An apparatus is described for measuring the power expended in driving a chain. A light-weight, compact, flexible structure is attached to the chain. The tension within the chain bends the flexible structure; however, the bending of the structure itself limits the maximum amount of force applied to this flexible structure. Thus, the bending of the structure will be limited and nonlinearly dependent on the chain tension. The structure is affixed to the chain such that any up or down movement of the chain is also experienced by the structure. A sensor on this structure such as a strain gauge or an accelerometer (or both) can be used to determine the chain tension. The apparatus also has a sensor to determine the speed of the chain's movement. A microcontroller produces the resulting power data which can be stored or directly provided to the user as audio, visual, or tactile information.