Abstract: Distance-measuring apparatus for attachment to a speedometer cable comprising a sensing assembly and a digital counter; the sensing assembly including a drum portion having a bore therethrough for disposition over an exposed section of the rotatable inner shaft of the speedometer cable, fasteners associated with the drum portion to secure the drum portion to the inner shaft, at least one magnet affixed to the drum portion adjacent a point on the periphery thereof, a housing surrounding the drum portion and spaced therefrom to allow independent rotation of the drum portion therein, fasteners associated with the housing to secure the housing to spaced ends of the sheath of the speedometer cable adjacent to the exposed section of the inner shaft, a magnet-responsive switch affixed adjacent a point on the periphery of the housing; electrical leads connecting the switch with the digital counter; the digital counter being capable of receiving and retaining a preselected constant value and adding the constant value