The US Air Force has put out a call for scientific proposals on the practical application of tiny drones that could surreptitiously 'paint' an individual with some kind of signal-emitting powder or liquid that allows the military to keep tabs on him or her. Or even upload the person's whereabouts to a hellfire missile. (http://www.dailymail.co.uk)
As explained in a Fox News Report, “Tiny insect drones, while not yet perfected, are gaining popularity in the military labs. From larger hummingbird drones to other tiny ornithopters to DARPA's remote-controlled beetle, the delivery system for such a technology isn't so far away from being a reality. What most of these tiny drones lack is range, which will evenutally improve with advances in battery life and materials science.”
To complement their remote-controlled insects, DARPA is further investigating 'smart dust' - a cloud of dust that could be sprayed into the air near a target in hopes that he or she might walk through the cloud and be tagged. Then the drone or delivery system would not even have to make direct contact with the target.
And why is the US Air Force interested in such technology anyway? The call for proposals notes that the technology will be useful for things like, em, tracking wildlife. Really! http://www.prophecynewswatch.com/2011/May02/0272.html