I am interested in purchasing a PLB and curious to listen to any suggestions, reviews, feedback regarding brands and/or specific models that anyone has to offer.
As has been pointed out by several responders, the best first step is recognizing the difference between a true Personal Locator Beacon (PLB), and a Satellite Messenger.
A true PLB operates at 406 MHz for 66-channel GPS triangulation and signal location, with a complementary 121.5 MHz signal for on-site Search and Rescue (SAR) homing and pinpointing within 100 meters. When activated, the perpetual signal it sends out is immediately captured by the first available high-altitude Cospas-Sarsat international rescue system satellite, usually within 5 minutes, and within 10-12 minutes at the most, and is relayed directly to SAR first responders who immediately take action. It is the same system used by aircraft and craft at sea (often mandated by the US Coast Guard). It includes a self-contained antenna and a built-in signal strobe light. A true PLB is not a toy, and it is not a gadget for social media updates or two-way communication. Nor is it a personal GPS device, digital compass, or flashlight. It is a single-purpose device specifically designed to reliably summon search and rescue in life-or-death circumstances in as short a time as is humanly possible. Cost is approximately $300 one-time, with no subscription, but with free NOAA registration (and 2-year renewals) required for user identification. It is factory sealed for battery and internal integrity, and must be reconditioned and tested (around $100) every 5-6 years by an authorized servicer. It weighs around 5 oz, and is roughly 4.5" x 3.5" x 1", depending on manufacturer. It is waterproof, and either is or can be made bouyant. Various types of PLBs have resulted in tens of thousands of rescues and saved lives.
A satellite communicator (Garmin inReach, SPOT, etc.), is a lower-power, low-altitude satellite interface device, designed to provide either one-way (outgoing) or two-way communication with friends, loved ones, websites, social media, or emergency contacts. It includes an "SOS" function to rapidly send out a distress signal and record its location, which then is relayed by satellite to a proprietary call center, which then attempts to verify the signal validity before contacting appropriate authorities and/or first responders. Even one-way satellite communicators can send an "I'm okay" signal at will, and can transmit "breadcrumbs" (waypoints) to an online map for others to view if they choose. The reliability of transmission by satellite communicators is not as robust as a PLB, and some even require a simultaneous connection among the device, a satellite, and a ground station before completing the transmission. Different brands use different satellite constellations (SPOT=Globalstar, Garmin=Iridium), and costs range from $150 to $450 or so, depending on features. All satellite communicators require a subscription at some level, and at least one brand has been known in the past for its overly tenacious pursuit of billing and collection (read many reviews before deciding on a brand). To their credit, satellite communicators have been credited with hundreds (if not thousands) of rescues and saved lives, and do not deserve the "bad press" some purists heap on them.
The lowest-level of a digital personal rescue device would be a plain ol' GPS, which won't signal rescuers, but it will let you know where you're in a really tight spot and perhaps help you find your way home safely, providing you have learned how to use it before setting out.
All of that said, I will confess that the very first digital device I purchased here in Colorado, where cell reception is nil in the backcountry (and after a lifetime of outdoor and backcountry recreation, including map-and-compass skills), was a true Personal Locator Beacon, even before a GPS. Once I leave the house, it never leaves my immediate possession in a pocket or on my belt. Period. Even while I'm driving, scouting a trailhead or campsite, quickly checking out a stream (which in Montana included encountering the largest black bear I've ever seen), or stopping for a snack. It is on me separate from my backpack, and it is tethered to me in some way while I sleep. It cost me less than most of my good REI gear, and it is cheap insurance against a worst case scenario.
Next, I purchased a GPS (Garmin GPSMap 64SC), because I do copious research and preplanning in BaseCamp and take a NatGeo topo map & compass wherever I go. Today, a Garmin GPSMap 66SE is a perfect fit for me -- but that's just me.
Okay -- now for my luxury (in additional cost as well as ounces) item: A Garmin inReach Explorer+. Why? Because my wife wants to know where I and my two teenage boys are, and that we are okay. I figure that if I bought a PLB to protect my life, why not buy a Satellite Communicator to protect my marriage? Ha-ha -- little joke there. But she makes a good point. I'm no spring chicken, and if I drop in my tracks or any of us need non-life-saving assistance, the inReach fills that bill, and provides her with perpetual tracking of our movements. It also provides the option of pre-programmed messages to fire, police, the Forest Service, AAA, or other non-lifesaving entities. So why do I carry a GPS when the Garmin inReach has a decent GPS onboard? Because the inReach GPS function is not as robust or as powerful as the GPSMap for on-the-fly navigation, and I'm a stickler for accuracy and flexibility. Again, that's just me. I suppose I could leave the GPSMap behind, but by now it's like a good friend.
Weight-wise, my array of products weighs in at an obscene (for ultralight types) 22 oz, but drops to 14.5 oz. without the GPSMap. But since the PLB is non-optional in my estimation, it is actually a part of my skin-out weight, and the others ultimately are expendable.
In summary, I have no particular allegiance to any maker of PLB, though I have been very happy with ACR's ResQLink+ product, and will probably go to a ResQLink 400 or View when my boys need their own. As far as satellite communicators, I'm happy with the Garmin inReach, but have never carried a SPOT product, so I can't comment one way or the other. Most important, PLEASE carry some type of rescue signaling device, and use for SOS-type emergencies ONLY when circumstances dictate radical, life-saving measures.
I have both an ACR Resqlink and the garmin inReach. Both definitely have there place. The resqlink is either on or off, and does not transmit any details other than I am turned on, and need help here. You need to have a very detailed trip plan with your contacts, because they will get called as soon as it is activated, and then a response will start. There are some famous stories of folks not updating travel plans or borrowing PLBs and then when it is used the rescue center is very confused, and it can delay the response.
It does have one of the highest powered transmitters thought. The inReach can be used to send updates to the world, and in the event of an emergency open a dialogue with emergency services. One can send I have a broken ankle, I am stable, I can shelter till evacuation, but cannot travel out without help, or can send, I have a patient with broken ribs/head injury/shock and need evacuation NOW. I am not sure how much faith I have in its water resistance, and always keep mine in a small drybox causing a weight , size, and signal penalty.
Sending Texts via a sat is far more efficient than a sat phone in a canyon, because it is very little data, and the device only needs a short exposure to the satellite to communicate.
The last time I did a raft trip down the grand canyon, I had both the ACR and the garmin. I had the ACR on my person the whole time (in my pfd) and kept the Garmin nearby, and on all hikes. If I swam/flipped the boat, I would have been separated from the Garmin, but, there was also mulitple inReaches on the trip. If I was solo, I probably would have that on my person too.
I initially used a Garmin GPSMAP device but did not use the mapping feature to follow tracks or routes so I switched to the ZOLEO device that is a GPS locator beacon and messenging device that had no screen. It links to a smart phone app but it can send out your location continuously without a smart phone. You can also purchase a SOS emergency service with just like the Garmin and Spot devices. Highly reliable, super simple, GPS locator and communicator. www.zoleo.com/en-us/