I have several ACR ResQLink devices I use for work. I have not had to use them, but they are light and have great capabilities. I also just returned from 3 weeks in northern Arizona teaching land navigation, and used the InReach from Delorme. They were great and maintained a good signal even deep in the canyons. It also allows two way comms, and the account is very flexible in how you manage the costs. There are two versions, I have the one that works with the Delorme Pn-60W GPS. Comms were great and I could track the students real time. It is a consideration. It also has SOS capabilities similar to a PLB, without the strobe light. It can work as a stand alone or with the GPS or a smartphone to communicate. I am very pleased with it.