LeeKooLuu T9 lighter-socket adapter with a switch

A lighter-socket adapter with a switch on it, six feet of cord. The switch is the reason it exists: a monitor wired straight into a 12V socket wakes whenever the ignition does, and after a week of that most people want a way to leave it off.

It also solves a smaller problem. A socket in a console with the lid down does not take a plug with a right-angle body, and this cord puts the plug where you can reach it. Twelve to twenty-four volts, with a fuse in the plug.