Bruce Schneier points to a paper suggesting using UV inks to tattoo keys to secured, implanted medical devices. Despite the legitimate problems involved with securing new devices that increasingly make use of wireless communication to enable richer, simpler monitoring, I can see one gargantuan flaw with this idea.
It is an obvious case of security through obscurity. There are some costs around gaining access to a target and fluorescing the key without tipping your hand. That is all that protects the key, though. The fact that it isn’t visible in ordinary light isn’t much of a protective measure. Maybe clothing alters the equation, somewhat, but I suspect not enough for the determined attacker.
There has to be a better way to allow emergency medial works to access these devices without painting a giant, if invisible, target symbol on your body.