People are incredibly intelligent and that means we are also incredibly scary. Check out more details of these guns here and here. For as long as there have been guns, there have been manufacturers who take ordinary objects and transform them into guns. Tear gas from a pen anyone?
The world is a dangerous place and undetectable guns and disguised guns are just another example of our ingenuity and that danger we possess. It's the same with drugs. Who would ever have thought we'd have to worry about people ingesting bath salts to get high? Or mixing chemicals in their basement to create the next ecstasy?
Another video to demonstrate the technology works?