Ideas are cheap. Good ideas are rare. Unimplemented ideas are worthless.
The point of a patent is to give an inventor a fair shot at developing his idea into something worthwhile, rather than just get stuck doing the legwork for someone else to just leap-frog over his hard work.
Interesting, though I did not understand things in detail rightaway. My first reaction if I were a potential kidnapper would be to buy a dozen of these things, get DNA from a couple of different people and make sure the place of crime gets contaminated with sufficient different and confusing samples that there would not be any evidence against me. An easier alternative would be to wear gloves.