About Taggant Bioweapons
Taggant bioweapons have been discussed as a theoretical possibility for a number of years; but (to the Sunshine Project's knowledge) never actually developed. The concept is simple, although there are many possible variations. In essence, a microorganism modified to exhibit an unusual behavior (for example, "glowing" genes, although in practice the trait would be far less detectable). A building, vehicle, or other object to be tracked and/or identified is then (secretly) inoculated with the bioweapon. The organism, which may or may not be deliberately destructive, is allowed to grow undetected. Because the organism exhibits an unusual trait, it can (theoretically) be detected by remote means, even if the object moves or is small and/or difficult to identify from a distance. The object's precise location can thereby be secretly tracked, facilitating surveillance and/or the targeting of a weapon to destroy it. In the Special Forces conception, these taggant weapons might also be engineered to be destructive upon command, for example, by triggering an inducible promoter system (popularly known as "terminator technology") that stimulates production of a corrosive agent.

The Sunshine Project
http://sunshine-project.org