GIT-R-Done is correct in grounding out the e-brake wire, that will work with most models and brands. but like SVT3Rivieres said the newest pioneer models avicn2 and avicd2 use the onboard GPS to determine whether the car is moving or not and disable the dvd function appropriately. There is a fix but it is complicated and requires soldering two points on the circuit board. peresonally not something i would want to try with with a 1500-$2000 unit.
