Maybe the FBI watches TED Talks...

[Kaido]

After reading about the FBI using drones for surveillance the USA, I came across this little gem:

http://www.wimp.com/powerquadcopters/

Just wait for the part with the nets

 

[Miramonti]

Reminds me of a handsfree mouse designed for disabled computer users that's been around for years. The user wears reflective tape or fabric, and the device uses infrared light to track it's position and move the mouse on the screen according to the user's movements.

Infrared light is emitted from the LEDs and is reflected back to the imager by a corner cube reflector (3M safety material). This reflected light is imaged by a CMOS sensor and the video signal is passed to the preprocessing electronics. The video signal is thresholded against a reference level and all passing data is sent to the USB microcontroller to send to the PC for object tracking. In order to increase the signal to noise ratio an IR filter that passes only 800nm and above is placed between the imager lens and the outside world.

The SmartNav can image any IR source; typically this is reflective material or an active IR source such as an LED. A user may track many different objects by placing reflective dots or LEDs on the object. The SmartNav has a 45 degree field of view and anything being tracked must stay in that field of view.

That appears to be the way these devices are tracked.