Earlier quoted context omitted.
It's a piece of molded silicone.
Cool gadgets can't be made of molded silicone? There's definitely more to it inside that's taking the scrollwheel motion and translating that to motion at the watches crown.. I'm personally curious what the gadget that does that looks like.
Based on this screenshot of the render gif you could argue at this point it's vaporware. The tolerances and geometry for the scrollwheel housing just don't make intuitive sense. Maybe we should get some actual footage of a prototype working?