coordinates of the asset tracking device 10 based on timing signals received from gps satellites the device 10 includes a wireless modem 34 such as a cellular or satellite transceiver for transmitting the location coordinates or other information to a central monitoring station the modem 34 may also receive communications from the central monitoring station a controller 30 which includes microprocessor hardware and firmware is connected to the gps module 32 and the to wireless modem 34 and controls the operation of the tracking device 10 a battery 36 supplies power to the gps module 32 controller 30 and wireless modem 34 the embodiment depicted in fig5 a includes a magnetic switch 28 in electrical communication with the controller 30 the magnetic switch 28 is preferably attached in close proximity to an outer wall of the housing 12 in one embodiment the switch 28 attains an open state when the switch 28 is in close proximity to a magnetic material in another embodiment the switch 28 attains a closed state when the switch 28 is in close proximity to a magnetic material in either embodiment the controller 30 senses the state of the magnetic switch 28 as being either open or closed thus when the outer wall of the housing 12 to which the switch 28 is attached comes in close proximity to a magnetic material the switch.