Systems and methods for monitoring a perimeter for ingress or egress by a member of an ad hoc wireless network. A wireless device is equipped with location means. In an embodiment, the wireless device is a cellular telephone equipped with a GPS chip set. A plurality of such wireless devices form an ad hoc network and are linked to a server in association with each other. The server receives retains perimeter boundary data and receives positioning information from each of the plurality of associated wireless devices. The locations of each member of a network are tracked relative to perimeter. A perimeter may be an egress perimeter, which defines an area in which monitored units are permitted to roam but from which network members may not leave. A perimeter may be an ingress perimeter, which defines an area in which monitored units are not permitted to enter. An ingress perimeter may reside within an egress perimeter. The system provides warnings when a perimeter boundary is approached or crossed.