https://en.wikipedia.org/wiki/Emergency_position-indicating_...
https://oceansignal.com/products/plb1/
You buy it, you never pay anything else, it works all over the planet, in extreme conditions, you never need to charge its battery (good for 7+ years), and most importantly, it communicates with an exclusive satellite constellation dedicated to search and rescue, operated by national governments. Your emergency call is handled directly by local government agencies, the military in many parts of the world, who have a duty to respond to the emergency - in accordance with international treaties.
https://en.wikipedia.org/wiki/International_Cospas-Sarsat_Pr...
For the US, it's on a state-by-state basis but rescue is usually free as long as it's a true emergency and you weren't blatantly reckless to begin with.
For other parts of the world, you might get a bill to recover the cost of rescue. But in most cases it's still usually free.
(Medical care once you get back to civilization is a different story.)
It costs about 50$ or so to register for the year and you just pay for a month when you need it. Well worth the secuirty. It also has a dedicated SOS button under a cap that you can press during an emergency. It will send your location to an international monitoring center that will dispatch someone local to your location for rescue. You can opt in for insurance that I believe covers an air lift.
It also can double as a location tracker or rudimentary GPS if you need directions to civilization or lake.
You can also get a older ELT-style 121.5 MHz but I wouldn't really recommend it. Might be nice as a last-ditch.
I test out my InReach every time I go out of cell service and it Just Works.
Setup was a pain though.
[0]: https://www.garmin.com/en-US/c/outdoor-recreation/satellite-...
EDIT: https://support.apple.com/en-us/HT213426
Covers many of the particulars.
I wear one a lot since I live alone in the woods without cell or internet service for several months out of the year.