What I did on my jensen unit is got a 3 position switch. One lead goes to the emgerency brake, the other lead goes directly to ground and the middle one goes to the headunit. It works fine and also, if a cop is near by, i can quickly switch it, so no ticket.
From the other forum I am on (the car club I belong to website)
Contura switches installed in dash for power door locks and brake override switch for dvd. The new one look very close to the factory ones.