I have a spot tracker. It turns out that there is no cell service just over the next mountain, only about 10 miles from our house. On my spot, there are 3 buttons, which I will call: "sos", "oh crap, come get me", and "check in Okay." Unfortunately when I had a medical issue just over that mountain, I only had the "oh crap" button set up to send an email, and my wife wasn't checking her email. I was really reluctant to push the SOS button, because it didn't seem like I really wanted emergency services. In retrospect I probably should have pushed it. When I got home, I immediately set up the oh crap button to send texts, and it does work. It sends a message and your gps location and also a link to a map on the spot site showing your location.
So I'm pretty happy to have a spot, even though when I really needed it I hadn't set it up correctly. The version with text service probably would be better, but I have no experience with that.