... currently seem to be the ACR ResQLink and the even newer McMurdo FastFind 220. They are very close in size and both are waterproof.
These are both 406 MHz GPS PLB's that use the dual, worldwide/military COSPAS-SARSAT satellite system. All 406 PLB's must meet stringent technical standards, including a battery that must last at least 5 years. This battery requirement is the reason that true 406 PLB's have either no or limited messaging/tracking capabilities. PLB's have no fees beyond the initial hardware purchase. Rescues in the US are coordinated via the US Air Force rescue network.
SPOT is not a 406 PLB. It is a locator beacon that includes significant tracking and messaging features. For that reason, the replaceable batteries can easily be depleted and must be closely monitored. SPOT uses a the satellites of the Globalstar phone company. There are annual fees, and additional fees for enhanced messaging and tracking features. Rescues are coordinated via a private company.
If all you want is "SAVE ME NOW" capability, a PLB is what you want. It has a much more powerful signal to reach satellites, with much more redundancy, and uses the most sophisticated satellite system available, the same one the military uses.
If you want tracking and messaging sophistication, SPOT can give you that in addition to a less reliable (but perhaps reliable enough) rescue message capability. There seem to have been a lot of recalls and technical problems with the various SPOT models, but I'm not an authority on what they have been.
Many outdoors people get both a SPOT and a PLB.
I purchased the previous McMurdo model, the FastFind 210, two years ago for a discounted price of about $150. It gives me peace of mind when paddling alone, as I almost always do, and even on local hikes or car trips.
Here are descriptions and videos of the ACR and McMurdo products:
You can find reviews of PLB's and other survival gear here:
Classic Freestanding Rack
1 Canoe/Kayak Trailer
Overstock Outlet Foods
Pull-Up Strap Handle Kit
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