Page 27 of the installation manual (http://www.wwstereo.com/_files/155788/documents/Kenwood--Manual.pdf
) shows a connection to the parking brake light circuit. It is the Light Green wire labeled "PRK SW" shown below.
If it is connected the way it is drawn, the PRK SW wire is connected between the lamp and the switch that opens and closes depending on the position of the parking brake (set or not). 12 volts is always present from the battery to the top of the lamp. It passes thru the filament to the wire that goes the top of the parking brake switch. So, when the brake is OFF or disengaged, the lamp is off and 12 volts is present on the PRK SW wire to your Kenwood GPS. When you set the parking brake, the ground (symbol is the funny slanted lines under a horizontal line) just under the brake switch passes through the switch and changes voltage at the PRK SW to "ground" or 0 volts. When this happens, the ground on one side of the lamp with 12 volts on the other side of the lamp - make is turn on.
So, what does this mean? Simply tie the PRK SW wire to any grounded metal and the Kenwood will think the parking brake is always set - for as long as it is tied to ground. You can check it with a simple voltmeter to be sure. Set the meter to 12 volts or more, touch black lead to ground & the red lead to the PRK SW wire. Kenwood should only work when at 0 volts (brake set). Release the brake - meter shows 12 volts & the Kenwood shuts off.
I hope this helps & Good luck!