1. In a long-term surveillance operation, apparatus for robustly sensing motion of an object, comprising: a CW radar for motion detection having an output indicative of detected motion; and, a sensor for sensing activity in the vicinity of said CW radar and for providing an output responsive to sensed activity, said sensor having a low power drain associated therewith; a unit for both turning on the CW radar responsive to sensed activity and for indicating the presence of a moving object upon outputs from said CW radar and said sensor; and, a processor for turning on said CW radar upon an output from said low-power sensor, whereby current draw associated with said CW radar is limited to times when there is an output from said sensor, thus to permit prolonged surveillance.