I suspect the EARL will not be able to meet the specifications for a PLB (hope I am wrong.) The original PLB concept using short burst signal to satellite, Doppler shift general location determination, 121.5 MHz for homing, and truncated GPS coordinates has been superseded by GPS advances, doing away with the Doppler and homing needs.
Full GPS coordinate transmission is still needed.
Perhaps EARL could integrate with the SPOT locater service, or position itself for other satellite systems.
Being able send a real (as opposed to canned) text message via a satellite (service) would be incredible.
Having the Garmin Rino capabilities of transmitting GPS location coordinates and plotting them on the receiving unit's screen would be useful.
Being able to direction find on a keyed radio transmitter would help SAR.
So would being able to transmit an SOS signal on a GMRS/MURS frequency, full power, automated, something SAR could DF on.