To test your USB-ports. For consumers, this isn't overly useful. This is what they write:

"Hardware designers of public machines should have a USB Kill to test their products: photo booths, copy machines, airline entertainment systems, ticket terminals, etc - anything with exposed USB ports should ensure that their systems resist electrical attacks."

Seems like a form of hardware pentesting to me, so for security experts and hardware designers, this looks like a pretty useful tool. :)