The palm-size ACR ResQLink+ PLB (personal locator beacon) fits neatly on the breast of my Type I life jacket using the supplied strap. It also fits inside an inflatable life jacket and can slip into my pocket when I leave my boat to pursue other adventures. Unlike an EPIRB, a PLB is not registered to a boat, but it does need to be registered.
I chose the buoyant model because floating is good. I also wanted the flashing strobe for added locating ability. The ResQLink+ uses two satellite networks along with an integral 121 MHz radio to alert responders and help them find the beacon. The 66-channel GPS makes location even more precise. It will transmit for 35 hours. $255.