QUOTE(Aggression @ May 29 2007, 10:56 PM)
im thinkin acouple of these and mount them on the side of the button
Those are about the exact same thing 101499 posted using earlier and are really for doors and windows, they're huge by comparison to the Guitars button. Not only that, they have a 3cm (1 1/4") operating gap, which means you have to get them around 1 1/2" away from each other before they will break contact, the button on the Guitar only travels about 2mm.
This may have to be done with a Hall Effect IC or a Reed switch and is getting to be more of a hassle the more I look for something suitabe, but I'm sure something is out there. A Reed switch is pretty much the same thing, just opens or closes when a magnet is near it, but finding one to open/close in that range is being a pain. The Hall Effect sensor isn't designed to handle a load, like driving all of those LEDs, so adding in some Transistors to do that part of it becomes necessary.