I made a cable pass, also known as a Shaft Passer, that you can wear like a necklace pendant or clasp. Bangles, rings, or string can be passed from the outside of the loop to the inside, without ever disconnecting it! The secret lies in the rotating wheel in the center.
If there's any interest in buying these, I'll come up with a better design (easier to assemble) and print some more! Thanks to Shapeways for fabricating this.