You looking for something that get global positioning such as a SPOT/ACR 2881 RESQLINK PLUS PLB375 (
http://www.acrelectronics.com/produc...qlink-406-gps/ )/EPIRB and sends emergency signal or a handheld VHF-like radio. The latter has more more limited transmission range but I went with the Horizon HX851 Floating Handheld VHF/GPS w/12 Channel GPS Reciever (
http://www.standardhorizon.com/index...8&DivisionID=3 ): sends a digital signal over VHF. I figure where I go I am never more than 3-5 miles from nearest potential rescue boat. You need an MMSI number. No annual subscription fees either.