Would be great to be able to pair this with a small solar charger.
Also, do these work internationally? I went scuba diving in Indonesia in a place with strong currents. Saw amazing creatures, but there was a story overhanging everything about some divers that had been swept away by currents, landed on an island inhabited with Komodo dragons & had to fend the lizards off by swinging their weight belts at them. They were found a couple days later, but badly sunburned and exhausted. Amazing!
My DeLorme inReach can send a message with coordinates and then doesn't need to remain online and continue transmitting. (Of course, you want to keep it online so you can continue to communicate with SAR, but if the battery were to die they would still find you as long as you don't move from your transmitted location in your emergency call.) So a solar charger, etc. wouldn't even really be necessary, and it will stay online for quite a long time between recharges.
Many long distance backpackers will carry high capacity USB battery packs to recharge devices off rather than a solar charger, as they weigh less and involve less hassle and can generally last between town stops every 5 to 10 days (depending on what trail, of course).
I'm not familiar with all PLBs/satellite communicators but my inReach works internationally.
Also, do these work internationally? I went scuba diving in Indonesia in a place with strong currents. Saw amazing creatures, but there was a story overhanging everything about some divers that had been swept away by currents, landed on an island inhabited with Komodo dragons & had to fend the lizards off by swinging their weight belts at them. They were found a couple days later, but badly sunburned and exhausted. Amazing!