House Wiring
All the tech gadgets people have these days all have their unique adapter that plug into the wall and then have a big wall-wart and then some DC power that goes into your gadget. Instead of this myriad of AC->DC converters, houses should have a central DC converter, and then along the normal AC outlets, there should be a common style 12VDC connector that devices can all accept and, if necessary, convert to a different DC voltage.
And while everyone is rewiring, there is another whole-house distribution system they should add. More and more devices (tivo, computers, etc.) have their own active cooling system. A house should be built with a central cooling system, like a reverse central vacuum, that pushes out cold air to sockets that are positioned around the house. The sockets could have an input and output, so the air would flow in a circuit, and the main cooling unit could run as needed. A proper system could be designed to run, or augment, your refrigerator and central air conditioning, as well as eliminate noise in devices in your house.