Yeah, I was wondering if the 457 kHz signal of the avy beacon was specifically chosen because snow was most transparent to that frequency as opposed to the 406 MHz PLB.
Hey, this website is called "equipped to survive", we're talking gear here. But, granted, nothing substitutes for common sense, training, caution, experience, preparation, situational awareness, and all of that other essential stuff. I've always travelled with a topo, a compass, and a backup compass.
So the consensus seems to be that each of the five pieces of tech I first asked about have a unique, nonredundant application that adds an increment of safety to my backcountry skiing expeditions. I was afraid of that, my pack's already too heavy.
This is also interesting:
http://www.skiingthebackcountry.com/beacon_malfuction.php, these folks have been testing cellphone and GPS interference with the avy beacon signal, seems to be substantial in some cases. Need to keep other powered-up electronics away from your beacon.