Patent ID: 7317927

Claim:
A method of selectively communicating with a first portable device within pre-defined geographical zones, comprising: defining a geographical zone utilizing latitude and longitude attributes; loading data representative of the geographical zone to the first portable device, wherein the data representative of the geographical zone includes the latitude and longitude attributes mapped to corresponding pixels in a pixilated computer image of the geographical zone stored in the first portable device; providing the first portable device with a ground positioning unit receiver, the ground positioning unit receiver permitting the first portable device to obtain geographical coordinates of the position of the first portable device; configuring the first portable device to determine the location of the first portable device in relation to the pixilated computer image of the geographical zone by determining a relative position of the geographical coordinates and the pixel data representative of the geographical zone; programming a microprocessor in the first portable device to determine the occurrence of an event related to a status of the portable device in relation to the geographical zone; and permitting the microprocessor in the first portable device to transmit an event message indicating the occurrence of the event to a second portable device.