Just to be clear again, unlike the lighthouse related stuff I've posted before, it's not actually my design. That said, I'm glad everybody that's tried it so far has agreed that it's an improvement to the experience.
I am actually thinking about modifying the design though. The existing one works fine and holds in place well. A bit too well actually for when I want to quickly alternate between having the headset on and off. Takes a bit of fiddling with my fingers to get the clip to release from my belt. Not the end of the world by any means, especially given that I usually put it on and leave it on for long sessions, but it got me to thinking about a quick release design.
The magnets I used for my lighthouse mounts should be easy enough to incorporate into a cable clip where the cable part magnetically latches to the belt clip. Should have enough strength to keep it together while moving, but easy enough to pull apart when needed without extra futzing.
Just watch out for accidentally wiping the cards in your wallet with a belt-mounted magnet, heh
I think I'd go for a padded clamp of some sort with an easy clasp. Could mark your preferred length on the cord with some tape or something.