So you put a couple of AA lithium batteries thing and then you start hiking and the folks back home can follow your trip up Mount Everest. There are 4 buttons on this little bugger, Help, ON/OFF, OK/Check, and 911.
The last one does exactly what you think it does, it contacts emergency services for you without the need for a cell tower. The device itself is waterproof, floatable, altitude-proof up to 21k feet, and freeze proof up to negative 40 degrees Fahrenheit.
Part of the device’s features is that with the $100 yearly service you can send your position back to an unlimited number of buddies, you just have to add them to the list before you take off. The device is $170 and there is an optional additional $50 yearly service charge that will get you noticeably more frequent position updates, lets say, every 10 minutes. Also, if you do wind up having to hit the 911 button, it will give those signals priority over everything else and will continue sending out the message for as long as possible, which is about 7 days when fully charged, hopefully you’re not dead by then.