A device to be worn by a subject for determining whether the subject is inside or outside of a containment zone, established by a user moving the device along a plurality of segments about the containment perimeter, the segments crossing the containment perimeter at an angle. There is a positioning unit for generating position data, including satellite positioning data, for the device. There is a processor unit configured to, while in a perimeter learn mode, establish the containment perimeter by receiving at least two segment waypoints from the position data for each of the plurality of segments, determine from the segment waypoints a containment perimeter waypoint for each of the segments and connect the containment perimeter waypoints to establish the containment perimeter. While in a contain mode, the processor determines from the position data if the subject is inside or outside of the containment zone.
