So, it identifies where you're at and allows a rescue. How is this not an emergency beacon?
It can be called a beacon as it does broadcast a signal requesting rescue, but as I understand it, the In Reach is more than just a PLB (Which only broadcasts an emergency signal continuously until the battery dies)
A PLB uses one set of satellites ( the International Cospas-Sarsat Programme, the international satellite system for search and rescue) and is more of a continuous broadcast in the blind (you don't know if your message was received) beacon
Where the Garmin InReach is a two was communications device which uses a different set of satellites (Iridium satellite network, same a satellite phones) to provide two way communication via text messaging. This later service requires a paid for contract similar to any mobile phone.
Both types of beacon will help get you rescued. The Garmin just requires an ongoing payment to provide service.