I used a SPOT for about 3 years, gen1 and later gen2. I wander off the beaten track often, and the wife insisted I use the electronic leash as she called it. Both it and the inreach system will upload breadcrumbs on a webpage so that others can track your location and movement. Spot also allows you to request help, or send short text messages. I never had to call for help, but a couple times sending a message out saying I'm okay, but running late kept people from worrying about me. Unfortunately, you don't know for sure if the message made it out, and I learned over the years that in some canyons etc it has connection issues.
For the last year I've been using an Inreach which I much prefer. It allows you to both send and receive text messages and seems to get a little bit better reception than the SPOT did. I wouldn't be without mine, as there is still an amazing amount of the US without cell reception.