This alternative is a good idea for the present, but someday soon (we hear) the FAA will outlaw any 121.5 transmitter and instead require a 408.0 alone in it's place. Of course the FAA has only extended the present rules to allow both/either for a short period (?) of time. I believe that 408.0 is required in any other country outside of the United States now. I also read that the non-certified ACK model ELT 121.5 will soon have an inter-changeable module that transmits 408.0 instead of 121.5. When that occurs I would expect that the prices on the rest of the 408.0's will drop a bunch. While I doubt that the Fed's will ever let us substitute the GPS transmitter as a stand-alone to take the place of their required 408.0 transmitter, the APRS surely would make flying safer - and a lot more fun.
Ed J. Mark L. wrote: One alternative to buying a new 408 MHz ELT is an APRS (plus your old ELT to keep you legal). The Automatic Position Reporting System is a ham transmitter/GPS combination that is mounted in your plane, and sends signals to the internet, which are then plotted realtime to Google Maps and Google Earth. Some of them have two switchable configurations, and you can set the second configuration to broadcast "emergency messages" which are automatically monitored across the world. When you go down a bunch of people know it almost immediately. Even if you didn't flip the switch before you went down, it wouldn't take long to find your last known position, which will likely be very close to your last transmission (depending on your location). The beauty of this system is that your plane and ELT can be ripped to pieces, but finding you (or your remains) would be dirt simple.
