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.
In episode 2.13 Houses of the Holy he is forced to stay in while Sam investigates, and he's spending 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: 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 and Sam, 2.13 Houses of the Holy
In 3.04 Sin City there's a Magic Fingers automat in the motel they check into, something Dean notes with delight.
The Magic Fingers returned in 6.02 Two and a Half Men - Dean indulges while babysitting in the motel.