The Satellite Messengers, while working similar to a PLB (with the SOS function), DO NOT have the same support in Australia nor do they work exactly like a PLB. They are similar at best.
- The Satellite Messengers (with the SOS function) require a COMPATIBLE & ACTIVE satellite, cellular or other communication network service plan to work.
A PLB does not require this.
- PLB's that meet Australian Standards + requirements are able to be directly registered for no cost with the AMSA (Australian Maritime Safety Authority) who are Australian Search & Rescue (SAR) providers. Satellite messengers cannot be registered with them nor can the SOS function.
- Satellite Messengers with the SOS function send SOS distress signals to GEOS International Emergency Response Coordination Center (IERCC) which is owned by Garmin.
https://www.iercc.com/en-US/about/PLB's activated in Australia contact local LUT's (Local User Terminals) & MCC's (Mission Control Centres).
https://www.amsa.gov.au/safety-navi...pas-sarsat-search-and-rescue-satellite-systemIf registered correctly, as they should be, the JRCC (Joint Rescue Coordination Centre) will then have your personal details, any notified trips, emergency contacts, vehicle/vessel details etc. already on hand (not coming further delayed through an international third party).
My opinion only but the best option in Australia is still to have a PLB & if going remote often a Satellite Phone also.
The Satellite Messengers are stuck somewhere in the twilight between both of these & are a lot less effective than having both a PLB + Satellite Phone available.
Not withstanding IMO they are still a good bit of kit with some great features but will be soon made somewhat redundant by 5G Advanced mobile network + phones.