After many years of solo overnight tramping and day walking in areas with no cellphone coverage I finally decided that it was probably a good idea to buy a Personal Locator Beacon or PLB.
If I am out and about and out of cellphone coverage and break a leg I can set this off and the signal will be picked up my two separate satellite constellations - one set at 38 000kms up in the sky and another set at 800 -1000km above me.
As I have registered my beacon the Rescue Coordination Centre New Zealand (RCCNZ) they will know it is a beacon alert is from me and attempt to make contact with me. Theoretically they should not be able to contact me as I will be out of cellphone coverage. If I was in cellphone coverage I would summon via phone.
Whether RCCNZ can or cannot contact me (or my nominated contacts) they will launch a Rescue Helicopter to come find me, so in other words I will not be letting this off unless it is a real and dire emergency!