yeah, like said above, sometimes you can just tie the emergency brake lead from the unit to a ground through a toggle switch, but it does depend on the brand/make/ model and year of unit.
The newer pioneer units have a motion sensitve gyro built into it so another bypas module must be bought on the black market...(EBAY). BTW Pioneer dvd owners should check out
www.AVIC411.com to get avic units to do cool shit