| 摘要 |
A method providing persons in a group information about the whereabouts of others in the group, including whether persons in the group have moved away from an associated vehicle. The method includes receiving information into a computer system derived from measured rf signal strength sent in digital form from one or more portable devices. The information indicates whether any of the persons has moved from a first relatively close position with respect to an associated vehicle and farther away from the associated vehicle than the first position. A timer function may be initiated if the received information indicates that a first person has moved farther away from the associated vehicle than the first position. Updated information may be received, indicating whether the first person remains farther away from, or has moved to a position at least as close as the first relatively close position is to, the associated vehicle. |
