Electronic Gadget Ideas for a New House?

pmadden asks: "I'll be building a house this summer (standard straw bale construction, earth plaster, the whole low-tech gig). Naturally, I'll be putting gobs of ethernet in the walls, with drops to the rooms, on the roof, and so on. I'll add wireless too, once it's secure enough to keep all of you out. What gadgets should I plan for, so that I don't have to do a major retrofit? I'll have cables for TPZ cameras, for when they get super-cheap. We'll leave niches for putting in routers and stuff like that. What else? What cool thing will be cheap in a couple of years, leading my wife to ask, 'why didn't you plan for that'? Any recommendations for good Christmas light control systems, and so on?"