Magic Fingers is the brand name of a bed relaxation system that makes the mattress vibrate. Dean is very, very fond of it, and delighted when he encounters it in various motels. It is mentioned by Dean in many episodes as a favorite form of relaxation, usually paired with some Casa Erotica or a copy of Busty Asian Beauties.
Dean: Did you bring quarters?
Sam: Dude, I'm not enabling your sick habit. You're like one of those lab rats that pushes the pleasure button instead of the food button until it dies.Dean: What're you talking about? I eat.
Dean is forced to stay in while Sam investigates their current case. Dean spends his time lying on the bed, letting the Magic Fingers "do their work." When Dean runs out of quarters to feed the automat, Sam isn't sympathetic.
Dean notes with delight that there's a Magic Fingers automat in the motel they check into.