Я имел в виду устройство типа такого.
Возможности:
(в частности, обратите внимание на непрерывную передачу по GPRS и минимум 20 сек. через СМС)
    * Support non-server based location
    * Location memorization
    * Auto location report
    * Authorize/delete the tracking phone number
    * Covert alert & voice surveillance
    * Geo-Fence: alert in case of breaching the predefined district
    * Movement alert: alert in case of movement
    * Speed alert: alert in case of excess of the predefinded speed
    * Power alert: alert when device is being switched off
    * Find Anyone! - place this device on an automobile, teenager, child, senior citizen, pet, you name it this device will follow it and tell you there exact location.
    * Works with Most Cellular Carriers - use your existing cellular phones sim card, and your ready to go. The iTrack is Quad-Band GSM 850/900/1800/1900 Mhz and GPRS TCP/UDP compatible.
    * Extemely Precise - when locating this device on Google Earth its accurate within 15 feet.
    * Last 48 Hours - the iTrack can last up to 48 hours and possibly longer depending on settings. It takes only 3 hours to recharge the lithium battery
    * Lastest GPS Technology - SIRF STAR III GPS chipset with 20 Satellite Channels
    * Magnetic Cover included - most vendors would charge extra for this include, but we find it only fair to provide you with the proper accessories
    * FREE Tracking Software - this device is compatible with Google Earth, you dont need to pay any monthly software fees like other trackers. Software Available at: 
http://Earth.Google.com    * Microphone Built-in: Remote spy listening/Spy Voice - track the person and listen in on there conversation
    * Realtime GPRS or 20sec GSM - GPRS is in real-time up to the second and GSM can be set to text message every 20 seconds
·         Auto-Tracking Setup the intervals you want the coordinance reported to you.
·         Authorize up to 5 phone numbers to receive coordinance or manage device.
·         SOS function: in emergencies press the SOS button and your location will be reported to the authorized numbers.
·         Geo-Fence: Alert in case of breaching the predefined district area.
·         Overspeed Limit: Setup a defined speed that you consider speeding and an alert can be triggered.
·         Low Power Alert: iTracker will report its low battery several times before completely dieing.
·         Shaking Alert: iTracker will detect if its in an accident and trigger an alert.
·         Electronic Lock: If the unit is physically turned off, it will send an alert before hand.