"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. :)
I am going to research for lockable USB dongles you can insert and remove only with a key.
You're in a coffee shop. Wouldn't the attackers just "accidentally" spill coffee on your laptop? Some laptops cope well with water from the top (over the keyboard) but not in the air vents.
The difference is deniability, you can always see that someone killed your laptop with coffee or smashed it with a hammer, with this you wouldn't know until you can examine the circuits.