Linked Necklaces

[atheniatrue]

I was re-reading Counting stars and it reminded me of a scene from a story, but I can't remember much about it. It was a Jack/Ianto story where they both wore necklaces that represented marriage/partnership. I think they functioned at least somewhat like the mental link and the rings in counting stars - they were created by another race specifically meant to link two individuals together. There was some sort of mental and/or life force sharing involved with them as well. I think they both had the necklaces most of the story, but no one on the team knew for quite awhile...?

The details are pretty jumbled and I'm not entirely certain that I am not simply mixing up multiple stories together.

Does anyone know what this might be?