I have looked into these devices.
There are basically two categories:
1.)Stay in touch, messaging, I'm ok, follow my path, I need help/SOS
2.) PLB - Personal Locator Beacons
The Spot and the InReach (supposedly better than Spot) are from type 1. More fun messaging, with potential to help you if in trouble. The issue with these types are that you need to pay a monthly/yearly subscription to use any of the features. Most importantly though is that they are not nearly as reliable at getting signals/messages out. If safety is the main purpose for someone then that is huge. Otherwise they are a fun gadget I think for sure.
The second type PLB's (several brands), are for I'm screwed, need help now situations. That's it. They are way more reliable at getting the distress signal out. They also have two frequencies. The first is the sat signal that gives rescuers your general area, then they have a homing beacon that rescuers can use when they are near the area to get pretty much right to you. Also no subscription for these devices.
So it really depends what you want it for. I know someone who used one of the InReach messaging devices and likes it, but personally I don't need to send "hi guys" messages when I'm camping or backcountry, etc. I'd want a PLB so I know I have a chance at getting rescued if something goes wrong.
Hope that helps!