Having never dropped my iPhone from a ski lift I consider myself one of the lucky ones, because apparently the problem is so common that Kenu created a kevlar tether to ensure a skier's phone never falls to its death.
The Highline's inner core, and the loop that secures the tether to your jacket, are both made from the same kevlar material that goes into bulletproof vests, so they can withstand up to 14kg of weight before breaking. It might sound like overkill, until the day it saves your phone's ass and you're happy they went with the good stuff.
Fully extended the coiled cable stretches 76cm, enough length to still easily use your phone in hand without it reaching the ground should you accidentally drop it. Just think of it as a bungee cable designed to provide peace of mind instead of terror-inducing thrills. [Kenu]