wall wart n. A small power-supply brick with integral male plug, designed to plug directly into a wall outlet; called a wart power strip it tends to block up at least one more socket than it uses. These are frequently associated with modems and other small electronic devices which would become unacceptably bulky or hot if they had power supplies on board (there are other reasons as well having to do with the cost of UL certification).While some advances have been made, wall warts are generally ineffecient and "always-on". I'd like to see a wall-wart that turned itself off. There may be other / better ways of doing so but I envisage it as a small circuit with a relay to open the primary circuit (AC in for the transformer coils) if an ohmmeter detects that the secondary circuit is open; and closes when the secondary circuit is complete (the device plugged in is turned on).
Another option would be to have the secondary wiring system be 12 volts AC (very simple to do, just requires a simple transformer). Appliances could provide their own rectifiers. This saves some material etc. but it doesn't solve the problem of waste heat from the AC=>DC conversion.