first of all... it would be helpful to know what mp3 player you have. I happen to have the nomad jukebox 6 gig player. It has built in backlights. o0(a sucky green) I will be changing them to a cool blue to match the casing as soon as I can find some blue ones that are the same. But anyway, I would assume that you could prolly run one or two led's from the batteries... you prolly have 1 or two right...? I'd say go for it, but expect a bit of a loss on the amount of listening time that you have.