Quite a bit bulkier, but with a lot more features is the Standard Horizon HX870 VHF hand held radio:
www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=85&encProdID=F074C5751E79473FCD911FF7D468A2E1&DivisionID=3&isArchived=0On top of being a full featured and unusually powerful handheld VHF radio, it still has the one button touch to send out an emergency signal with your GPS location, name, craft, and inland emergency call numbers. It also allows you to talk to rescuers or other paddlers and boaters over VHF, allows discrete calling to other MSCI registered radios instead of open channel hailing, it is waterproof and also floats with a water activated strobe light that turns on to help you find it. It has a nice feature where you can send, or request, GPS locations to other VHF radios which will happen automatically without anyone needing to answer, and this one will display the compass course direction and distance to the other person's location. All this for about the same price as the PLB. My wife and I carry these on all of our downwinders on Maui.
As a cautionary tale, a husband and wife who are experienced paddlers were doing a Maliko run a few weeks back. She forgot to put on her leash and lost her board. He realized that she was missing and had no idea where she was. He paddled a mile back to land, and borrowed a cell phone to call emergency personnel while having no idea where she is. Meanwhile she is trying to swim in from a mile out in very rough seas with no flotation and no communication. Luckily she ran across some divers who helped her swim in until they flagged down the lifeguard on a jet ski. Very experienced paddlers, but how many things are wrong with this picture that were probably saved by the luck of the divers being there. Think of how many ways they could have used the HX870 to solve this situation. They could have called each other, he could have gotten an automatic location fix on her with course heading and distance even if she was not able to operate the radio, either one of them could have hit the emergency button and gotten a return call from the coast guard so that they could describe the situation, and the lifeguards would have her GPS location so that they could get straight to her on the jet ski.