Having been a member of Fire & Rescue service long time, I must to say the idea is good but not feasible!
The standard protocols for incoming calls is wide known in the fire, rescue, EMS and dispatchers community across Europe (even with the Brexit...).
They are based on information reliability and a number of questions is asked any time a call arrived.
With a PLB/EPIRB the protocol is clear.
Answering to a call is a team work that involves dispatchers, fire personal, ems and often helicopters, police and civil protection, at least.
The decision to send one or several agencies/vehicles is based on the amount of information, expected arrival delays and severity of the problem. Sometimes is an educated guess taken by officers with a lot of experience.
But, most important, is based on "standard" emergency calls.
That's why the emergency calls from ships are handled by coastal stations an not by PSAPs.
So, if one look into the RBNhole and sees an SOS, what should he do: Call 112 or 911 if located in North America ? Tell them what ? What is the nature of the emergency ? How many people need assistance ? Where is the emergency ? Who am I (liability) ? etc, etc...
The number of questions that arise and liability connected with such an kind-of-alarm system is huge!
Saying so, I'm with Andy and Andrew.
PLB/EPIRB is the way to go!
Vy 73 de Pedro, CT1DBS/CU3HF