Roy Smith wrote:

It depends on what you're using it for. A handheld GPS and a ham sandwich
are both useful objects, but using either one for the other's intended
purpose can be dangerous.

Well, there are those stories of the open-cockpit airmail pilots using
cigars to time approaches. Don't know about ham sandwiches though. I
suppose if you're Steve Fossett, and your sandwich starts getting
moldy, you're about to run outa gas.