I use 2 different GPS trackers for my toys. Both of them use a GSM SIM card to communicate with your cell phone
. You can set a geofence and if the unit moves outside of the fence, it transmits a text msg to your phone
with lat/lon and a link to google
maps. One of them is a TK102B. It has a battery
in it that should last 3 or 4 days, so if the main source of power is removed, it will still transmit. It will also listen and let you hear what is going on inside the boat. About $30-35 on Ebay. The other is the GT02A. This one does all the same except no listening, no battery backup, but it is waterproof. It needs a constant source of power, if they cut battery power, it no longer works. It's also about $30 on Ebay.
If you need professional tracking services, you can contact Airsis (Portvision) which provides real time fleet marine
tracking worldwide. A little more expensive, but their units transmit back via satellite
, so if your boat is taken offshore
beyond cellular range, theirs will still work. They have a website showing the location of your unit, and you can rewind and follow the tracks from the moment it left the dock
. Theirs uses Lithium AA batteries, they will last 6 mo to 5 or 6 yrs depending on ping interval.