How to keep my keys in the ignition.

Although haven't had someone do this maliciously (yet) but find it pretty annoying that someone can just pull your keys out of the ignition willy nlly and kill my bike while I'm riding. know a couple guys who've had their keys snatched leaving them stranded and others who get pulled over and cops immediately pull them out. Not a fan of either of these scenarios. Does anyone know any tricks or mods that will keep my keys in the ignition unless I want them out myself?