[llajumpvid]

The n dash DVD players like the Kenwood and Pioneer Flip up say DVD use when stopped or in park, does that mean that my passenger can not watch a DVD while I'm driving?

If installed correctly (meaning leagally) then yes your passenger is SOL. You can probably override the feature by grounding to a constant ground. Installed correctly it is probably grounded to the parking brake or transmission. Have the installer tell you "which wire shouldn't I ground to make sure the safety feature isn't overidden?"