I'm wearing a magnetic ring (a post on LW gave me the idea). It's fun, and I can take it off whenever I want to. Occasionally it comes in useful too; when I need to open up my computer I can put the little screws on my ring, and I can tell whether a pot will work on my induction hot plate.
This sounds like a much lower-commitment variant, but it doesn't seem like it would have close to the same sensitivity.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.