If you're a former Russian spy and you're worried about being poisoned by your former employers, going out to eat has got to be a harrowing experience. I mean, how will you know whether or not your food has been poisoned with some radioactive material such as Polonium?
Why, you just get one of these Polonium Pens, of course! Designed to detect the spy-murdering substance, it'll flash a little LED light at you when you hold it over food or drink if it happens to detect any Polonium. If it does, I suggest getting the hell out of that restaurant as soon as possible and watching your back.
Shout out to commenter Emockler for noticing the pen first.