One of the interview questions where I work (we do automotive electronics) is "Explain how GPS works." It's directly relevant to the job, but it's also a neat opportunity to see how someone sizes up their audience, manages time and assumptions, etc.
All those things are neat, but mostly what I've learned is that quite a lot of people, otherwise apparently reasonably smart and competent and toting a whole stack of prestigious degrees, have ghastly flaws in their mental model of what GPS is.
