US Patent 6850839 Time-sensitive article tracking device

An article tracking device that can be attached to or otherwise located with movable and non-moveable articles has a memory that stores a subset of spatial zones and corresponding time intervals during which the spatial zones are valid. The device is adapted to periodically read the current time and its current position from the position determination system and to determine whether a spatial zone corresponding to the current time exists. If a corresponding spatial zone exists, the device determines whether its current location is within the spatial zone and performs an action in response to this determination.