If you're truely going off the grid and want realtime coms available there is no alternative to Iridium.
An EPIRB is great if you just want to be found.
Argument against Globalstar is that it is not a true polar to polar real-time solution like Iridium.
Iridium is the only constellation where you will always find a bird overhead anywhere on the globe (with a ground station relay)
Realistically, Iridium has occasional (~5min) signal gaps likely due to the aging constellation (based on my own use cases developing with a roof mounted antenna)
If your GPS can get a fix, you can probably find enough signal to send a SBD.
Iridium carrier signal is stronger than GPS.
Likely the satphone is better, but there are still limits.
Why not? There are all kinds of Emergencies. Some trees are fairly easy to climb.
Another problem with that is the current public perception often is that their phones contact space. I hear this over and over again. It is interesting. Drive by cell phone towers all day and still think your iPhone is "going to space" when it is loading slow. There is a Louis CK bit about this on Conan's show. I wonder if that kickstarted part of the misconception
Have you seen the Louis C.K. bit the parent is referring to? It's a joke, but the joke is that people are annoyed with their phone being slow despite it "going to space".
Scared all the elk away...
Recently, the strangest thing that happened to me was having a signal on a total wi-fi phone in a remote area while friend's verizon phone plan had no signal. This was an area where there were no houses ...just miles of land.
If you're on the edge of signal you'll lose data and voice then SMS last. Mainly because SMS is small enough to slip through in 1-5s intermittent connections. UK Emergency services and mountain rescue use SMS extensively, but backed up by other channels - radio, sat phone and what have you.
So I could perhaps understand a cut-down text device, but voice? Hmmm. Even a 121.5 transceiver, cheap and AAA powered, would be a better idea.
Speaking from very personal experience, as in I was living on a high spot in Joplin, MO right at the southern edge of the "zone of total destruction" when the 2011 tornado hit, one cell tower hit the stack of apartments to the east of me, and the other landed on part of the parking/access road area just to the west of me.
ADDED: I forgot that the "before" picture I picked up (from the eeevil Daily Mail, this is one area where they excel), shows the original positions of the towers: http://www.ancell-ent.com/1715_Rex_Ave_127B_Joplin/images/
From the perspective of the picture, east is up and a bit to the right, the towers fell up and more to the left (counterclockwise).
But tornadoes have several saving graces, including that their path, even for an EF-5 monster like that one, is relatively narrow. As in I could walk beyond its effects, only a few blocks north, and while I can't remember if I had still had cell service while in my trashed apartment, I easily had it once I'd relocated to my mother's home ~15 block north of the path.
2 days later, I think it was, I was able to return, and by then AT&T? had a temporary cell tower running on a generator next to the spot of one of downed cell towers, using a point to point antenna to connect it to the rest of their network.
This characteristic allows massive surging of resources to the affected area, e.g. as I left my apartment complex within 1-2 hours, fire trucks from 40 miles (Lamar, distance by road) and 21 miles (Quapaw tribe in Oklohoma, with which the city has a close relationship) were there and men were already suiting up to search the complex.
I grew up there and my folks still lived there at the time not far from St. Johns Hospital (the one that was hit and featured in most of the news).
I was working at a startup in Oregon when a friend in Joplin called right after the tornado went though town. A quick look at the news told me all I needed to know and I immediately packed up my Jeep with emergency supplies and headed out for a non-stop drive from Portland to Joplin. I got there late on the 2nd day and the place was still in shambles. No cell signal in the disaster zone at all. My folks house was spared major damage (neighbors on either side and behind weren't so lucky) but they lost power, cable, and land-line when a falling tree ripped the feeds and power meter off the house.
I had an AT&T phone and it was mostly useless for about a week. Even after the temp towers went up (and there was one not very far away) the network was saturated with emergency workers. OTOH, my Iridium worked just fine. Too bad my folks didn't have one -- I didn't know their status until I got there in person.
I'm don't see a whole lot of value in a device like this. Any sort of natural disaster is likely to tear up the infrastructure a traditional cell phone depends on.
Although I think I recall it not being bad in subsequent weeks, and, I would be using it from the edge of the zone of total destruction, and a hundred feet or so away from what was likely a tower of my provider. But I wasn't using it heavily there, at most for coordination while on-site removing stuff from my apartment.
You were also several miles to my west, in the direction the tornado came from. I also had the advantage of being on a hill, that might not have been true for you.
But we agree in that such a device is not to be depended upon; I'd say at best something to hold in reserve, and mention of affordable emergency Iridium systems like https://news.ycombinator.com/item?id=11701692 has gotten my interest.
If we assume a 50% charge at crisis start, and a rational response by the person using it: * Turn off wifi, cellular data, bluetooth, other unneccesary stuff * Turn screen brightness to minimum * Send only text messages * Don't use phone unless sending or receiving important message
any decent smartphone will last 4 days or more.
Example: I have a midrange Samsung A5 for an office phone (mandatory company rules). With wifi and 4G enabled, but only being used to check the occasional message. It lasts 8 days on a charge.
121.5 Mhz Emergency Channel is for aviation usage only (other than older PLBs) although if you had a multi-band handheld transceiver (in a genuine emergency) it would probably be useful to communicate with rescue helicopters etc.
I'm not current with aviation any more so the off the cuff thought could be very silly. :)
Using aviation channels for frivolous non-aviation uses can result in FAA/FCC/FBI getting involved.
The 121.5 beacon actually interferes with Emergency voice transmissions, so downed pilots sometimes shut them off in order to talk to rescue crews etc. without a beeping noise :)
In the US at least every phone has to be able to dial 911 even if it doesn't have a plan (all it needs is a SIM card). Useful for having something in an emergency if you're on the road or some other place near cell service.
I was under the impression that a SIM card is not required. Am I wrong?
If the phone is not connected to the network currently, it will do network hunting, and will be able to do an emergency attach to the first network it finds. This may also happen if your say out of coverage with your own provider, but can see signal from another provider, even if there isn't a roaming agreement. 911 get's interpreted by the phone in a special way, and the phone will flag the request as for emergency services when connecting to the network, so the network will treat it with priority. In theory, even if you can't be delivered a phone call, or the network is overloaded, emergency calls should still work, depending on exactly what the problem is of course.
It's also something that at least here in Canada, get's tested fairly extensively, both on all the devices we sell, and the network equipment when deployed and each patch.
* my views are my own, and do not reflect those of my employer.
In some European countries (France, p. ex), a "valid" SIM card is now mandatory (too much prank calls).