The system beams a keyboard or menu onto the user's forearm and hand from a projector housed in an armband. An acoustic detector, also in the armband, then calculates which part of the display you want to activate. via Body acoustics can turn your arm into a touchscreen – tech – 01 March 2010 – [...]

And then puts them into a database accessible by… who? and why? This started in 2002 and has been going on without your knowledge ever since… Newborns’ blood used to build secret DNA database – Short Sharp Science – New Scientist.