My wife Kat and I own and use a SPOT device when out in 'the bush' working. It is inexpensive to both purchase and subscribe to the service...you basically set up some email addresses to which the SPOT will send your OK or help messages. The 911 button results in a call to 911 that includes your GPS coords and also sends a message to your emergency contact.
Really simple and cool technology that played at least some part in saving Ed's life.
Highly recommended for anyone out there in remote places, alone or not.
I have a PLB (personal locator beacon) I used to carry in my boat. I saw them advertised for outdoors people, not just boaters. Maybe I should dig mine out of the junk box and start carrying it in my fanny pack! One of those things you never need until you need..