Source: http://gizmodo.com/a-headphone-jack-laser-pointer-that-no-one-will-be-able-1450204782
Don't let anyone tell you otherwise; highlighting a character's crotch on-screen at the movies is hi-larious, and always will be. But getting caught with a laser pointer in your hand and tossed out of the theater isn't. So thankfully red lasers have been around for decades, and have been miniaturized to the point where they can hide inside your smartphone's headphone jack.