this is the one i got http://kti.com.au/safety-alert-plb/ has a fairly decent antenna that wraps around the unit and easily fits in top pocket. GPS and 10 year battery life was a plus for me, and obviously works out good on the cost over 10 years as you only buy the unit - no ongoing fees. about $250au from memory plb uses 406MHz COSPAS-SARSAT - some info - https://www.cospas-sarsat.int/en/18-frontpage-articles/603-what-is-a-cospas-sarsat-beacon registered mine with the Aus government you set up an account / login with them - you give them your details and stuff like next of kin etc. you can input trip details if you want. hope i never need it or use it.