Abstract: In one embodiment, an apparatus comprises a mount, a housing, and a sensor, wherein the mount is adapted to be secured to a shoe, the housing is adapted to be releasably attached to the mount, and the sensor is supported by the housing such that the sensor remains supported by the housing when the housing is separated from the mount. In another embodiment, an apparatus comprises a mount and a motion-sensing device, wherein the mount is adapted to be secured to a shoe, and the motion-sensing device is adapted to be releasably attached to the mount.