it's basicall the pickups pots, switch, jack, all the wires and any thing like the fernandes sustainer kit
everything including pickups, tonal and volume knobs, pickup selectors, ground wiring.....basically anything electric on your guitar
I'd say there's not that much in a basic guitar, (electric) It depends how many different controls there are. If there's a tone knob, or two, or if even more probable a volume,or two, nearly all have that one... Exceptions of course, but why not keep it simple? So that would mean the necessary wiring for, let's say the pickups > volume > the jack > amp. Did I miss something?

Hehe, or maybe a Gibson Robot, that's a little bit to much xD