Specific Tweak

So I'am looking for a specific tweak, hopefully doing some forum searching someone might have a solution. I just built an ipad dock pretty much for my car and it will always be connected to the auxillary and a charger.

Pretty much since it will always be connected to the charger, I want a tweak that will have the iPad turn off once it loses connection from the charger (ie once i turn the car off since the charger will then turn off). Anyone know of any tweak that has the device power down when not connected to a power source?