Yes, it is great that technology (and finally the US Gov't -- the last to approve PLBs) have made these avaiailable as personal locator beacons.
My Breitling Emergency watch has the 121.5 MHz homing beacon -- about as portable as you can get. However, in February, 2009 -- the COSPAS-SARSAT will
no longer monitor the 121.5 MHz frequency. Only beacons equipped with the 406 MHz transmitters will function with the satellite system after that date.
So, all of the boat and aircraft equipped with the 121.5 MHz -only ELTs and EPIRBs will no longer activate the COSPAS-SARSAT system (you'll have to buy a 406 MHz beacon). Search & rescue aircraft will continue use the 121.5 as a homing frequency -- once activated for a search -- but it will no longer be the frequency that activates the system...
For more information:
http://www.cospas-sarsat.org/FirstPage/121.5PhaseOut.htm