I still have a pair of the orange Salomon safety straps, like newfydog's. I don't get to use them at all where live, though. To confirm both his and SpikeDog's comment, there is some potential danger of a 'helicoptering' ski when using these, but I wouldn't think as much in deep powder. I have firsthand experience of this danger on the hard(er)pack.
Back in the day,(when everyone used 'safetys' and Scott Brooksbank was king) I was skiing the local hill one day, doing laps on the powderless. (We used to build jumps regularly to break the monotony of skiing the 'boring' terrian here in the Midwest. Ahh, the joys of youth!) I had been lapping a particularly fun jump for awhile that day when I overshot the landing area(speed kills) coming out of a back-scratcher, where the hill flattens out rapidly. Well, I landed my right ski fine, but I was a little short with getting the left ski back under me and the tip dug into the hard-pack a few inches, snapped off and helicoptered left in an off-axis arc, whirling around like a yo-yo on a short string, nailing me across the back of my head, thanks to those 'safetys'. I probably looked like one of those hoverboats, with my left ski as the propeller!! I was OK, but there was enough blood to scare the heck out of the beginner ski school class when I came walking by, sporting a guaze 'headband' with a big red spot in the back!! I guess that makes a good case for why you wouldn't want to have the ski-school staging area right next to the patrol shack entrance!