This is bloody fantastic and, also, terrifying. Was browsing the DARPA website (as you do) and found that the U.S. government is researching how to detect people uniquely in large areas or large crowds. This is of course designed for tactical strikes against enemy combatants, whereever they might be using a “unique and exploitable chemosignal” which presumably can be detected over large areas.
Imagine a system of chemotype-detectable satellites that use their cross-referential data to locate individuals globally – Al Quaeda should be scared, but so should everyone once the government changes the laws – imagine such a technology in the hands of a totalitarian regime.
(I also had a look at the “Special Projects Office” which perversely seems the least special part of the centre. Pretty useless, generic information.)