[oldbbsnickname]

Don't expect it to work anytime soon or to supplant EPIRBs.

Even E911 locating in the US just doesn't work at all with nonzero and unknown combinations of phones, carriers, and jurisdictions. US LEOs have almost universal, real-time locating ability from N km to sub 1 m accuracy if it's in range of a single tower of any phone without a warrant. If a phone can send an SOS to a comm satellite, while there's a recent good fix from 3+ GNSS satellites, then that's useful.

The risk to avoid will be over-reliance on a consumer grade cell phone as a substitute for the ruggedized and proven EPIRB system.