Research laboratories envision tools that could identify and track just about every person, anywhere — and sound alarms when the systems encounter hazardous objects or chemical compounds.

Many such ideas seem to leap from the pages of science fiction: An artificial nose in doorways and corridors sniffs out faint traces of explosives on someone’s hair. Tiny sensors floating in reservoirs detect a deadly microbe and radio a warning. Smart cameras ID people at a distance by the way they walk or the shape of their ears. And a little chemical lab analyzes the sweat, body odor, and skin flakes in the human thermal plume — the halo of heat that surrounds each person.