HMM. THE AIR FORCE has "issued a call for help making a miniature drone that could covertly drop a mysterious and unspecified tracking 'dust' onto people, allowing them to be tracked from a distance. The proposal says its useful for all kinds of random things, from identifying friendly forces and civilians to tracking wildlife. But the motive behind a covert drone tagger likely has less to do with sneaking up on spotted owls and more to do with painting a target on the backs of tomorrow’s terrorists."