Omni was a pop science magazine that looked as if it were published by a softcore pornographer, because it was. (Bob Guccione of Penthouse, et al.)
Anyway, there was a blurb for a product: "Galactitags" -- dog tags stamped with the pulsar map that's on the Pioneer plaque. The gimmick was that, in the event you were abducted by aliens, if you managed to escape and flag down a Good Samaritan alien, the pulsar map would be enough to guide you back to Earth. (Additional gimmick: Money-back guarantee if the tags couldn't get you back to earth.More in a 1987 NYT article about various gimmicky things.)
It was peace of mind of sorts, for only $11.95 (or so) plus shipping and handling. Also available in gold or silver plate.
Also naturally, I had to have them:
Now, the clinking and rattling got annoying after a while, so I put some rubber silencers on them. Also, because of metal allergies, I had to swap chains and cut some clear plastic report covers to keep the tags off my skin. It got very complicated.
Anyway, I still have them.
The Galactitags.com domain isn't active right now, so I don't know if you can still get the originals, but there's at least one, similar knockoff: Location Earth Dog Tags.