The skimo tether is based on an idea from an IFMGA guide. She she would have her clients hitch a double runner to their harness and then clip it to the top of their shoulder strap. The purpose was to make another attachment point that was likely to be accessible if they fell into a crevasse while unroped, skiing on a glacier. There are several stories about people being stuck such that their harness was inaccessible, or partially buried in snow. Having an attachment up by the person's head would speed up extraction in these scenarios. Having a very light and strong device like this is useful for a myriad of jobs when performing a rescue. 
 
The Skimo Tether is the lightest solution I could come up with. Made from 4mm dyneema it has a breaking strength of 14kn and my 35-inch version weighs 14 grams. Each one should be custom-sized for the user. One end has a soft loop to hitch to a harness, the other has a stiff loop to make it easier to clip. I keep finding other uses for it; It can be a rappel extension, or a draw, and I use it as part of my ascending system. 
 
To measure for it, put on your harness and your ski pack, probably with whatever layers you wear skiing. Take a double-length sling and hitch it to your harness. Then take a carabiner and figure out where you want it attached to your pack. Then tie some knots in the sling until you think it is the right length. Fiddle with it until you are confident, because there are no returns on custom products. Then un-hitch it from your harness and measure the overall length of the loop.