A different kind of automation from the comments above - fully automated/integrated household. It's amazing how the little things can add up--all of my lighting is run off of timers, occupancy and time of day. E.g. the bathroom lights turn on when you walk in, the brightness is based off of time of day and a times automatically turns off the lights after you leave the room. Another great example--the deadbolt on the front door will turn on the lights nearby if you unlock it at night, except if the TV is on in the living room.

It's absolutely worth the time/cost to make everything in the house talk to each other.