Ahoy! I'm in the process of making something I wanted to do for a few years, namely, discrete wearable key pairs. A long time ago, Charlie Shrem had a ring with one of his private keys engraved into it, and I thought that was pretty neat, sort of like an emergency access to some coins just anywhere on the go. I got caught up with the technical details, and dropped it to move onto something else. Anyway, the other day I learned about a new feature in the 3D modeling software that I use that would allow me to get past one of the issues I had with the idea. The other problem I got hung up on was obscuring the keys. I experimented with using a lesser purity alloy to fill in the engraved letters. When exposed to high heat, the metal would melt out, exposing the keys. While its possible, its not really feasible for a number of reasons. Anyway, after trying out this new modeling feature, I decided that fancy security features on the physical side may not actually be needed. A private key could be encrypted before being engraved, it could be a riddle that leads you to the GPS coordinates of where you buried your paper wallets, unintelligible gibberish, or anything else that could be imagined could be put on it. Shrem's ring had his keypair minus one character engraved on the inside for example. I'm confident that a suitable security measure exists to mitigate risk.
Would anyone be interested in something like this? As pictured, I can currently make them in silver, any karat or color of gold, and pretty soon Platinum. The images below were just a preliminary test to make sure the lettering was sufficient, and that I could put something other than text on it. Its just a standard boring ring, I'll make some more interesting design wise, but for mine I'm personally undecided whether boring and unassuming would be more secure than flashy.