I’ve said it before on here and elsewhere, but I do really feel like the way that SPOTs are marketed really misses the mark and misses the areas where they really may have some value.
Although I’d certainly press the “SOS” button if I fell off a cliff while getting bitten by a rattlesnake and mauled by bears, I don’t really view the SPOT as anything close to being my main way of dealing with a problem of that nature, especially for a lot of the hiking I do, which tends to be on one of the long trails, in the National Parks, or somewhere else where there are probably people or I have reasonable prospects for self-rescue. Staying near a trail and flagging down some passers-by is likely to get me more speedy effective assistance than shouting “HELP!” into the heavens and hoping a helicopter shows up in a couple of days.
Where I get the value out of carrying the SPOT is the ability to signal to the folks at home that I’m all right. Although I’m withered and old at this point, I still have parents that worry about me, and the 4oz of a SPOT (and the annual fees) are a small price to pay to keep them feeling better, especially since they’re often helping out with things like mailing boxes, airport rides, cat care, etc., etc. When I’m on leave from work for a longer trip as well, my coworkers (who are picking up my slack while I’m gone) also get a kick out of seeing the little marker move north. It’s a nice thing for the people in my orbit who are helping me in some direct or indirect way.
The other place where I’ve gotten REAL value out of the SPOT in the last couple of years is my custom message, which is “I am fine but am no longer following my stated itinerary,” which is my bailout message. I’ve had some pretty bizarre injury/illness issues come up in recent years (including 2 ER trips in the span of one hiking season), and sometimes my return to civilization has taken me via routes that no sane person would expect me to take based on my itinerary, and where no one would necessarily think to look for me if something happened. Sending a signal that I’m doing something unplanned (usually at a trail/road junction) and throwing on the full tracking mode at least gives the people at home the opportunity to put 2 and 2 together about what’s going on and where I might be going. As someone who’s almost always hiking solo, I do try and make sure that there’s always someone who has some idea of where I mean to be going, when(ish) I mean to be there, and when I’ll be back, and the SPOT really helps with that for times when the unexpected happens and I’m not where I said I’d be. When I’m hiking out on a 15-mile side trail that I didn’t plan to take and then hitching 20-50 miles to a town I just learned existed, I do take some comfort in the folks at home having some inkling of where the heck I am.
Is it critical/essential gear? Of course not. Is it useful enough to justify carrying it? For me, yes.