If you do go the route of using personal locators do a google search and learn the difference between SPOT and PLB. They are entirely different animals. Here's a few highlights of the differences and a more informed link.
SPOT is cheaper than the others initially. There is an annual fee to use the system, and with additional features the cost climbs. PLBs cost more upfront and the batteries are more expensive but no annual fees.
HOW IT WORKS
Upon activation, SPOT sends a signal to a satellite with your location. You can also send messages via SPOT that you can't do with most PLBs. That signal is then sent to Globalstar (private company) where they will send the message out accordingly. Either to authorities to come get you or to whoever you wanted to contact. Works very much like a contracted home security system.
Upon activation of a PLB, a signal is sent to the satellite with your location. In addition a homing beacon is being transmitted from your location to all the search and rescue teams in your area monitoring the frequency. These signals go directly to the authorities USAF, CAP, and other agencies. They are required by law to find the device.
SPOT hands down. Keep in mind the more features you include on it the more your annual fee. Some PLBs have features, but for the most part don't come with anything close to that. They are activated and you wait for help to arrive.
OH CRAP MOMENTS
As said earlier, PLBs go directly to the authorities. They are coming and there is no way to call them off. So you better well be in jepoardy or you can be susceptible to fines. PLBs also have stronger signals and can pinpoint your location much better than SPOT.
SPOT you can send messages to call off the search if you rescued yourself. You can call towing services etc, if your life isn't in danger and maybe you just broke down somewhere. Your location is not as defined, but you have the ability to send directions.