** I successfully did this on my '08 Dodge Ram 1500 with a Pioneer AVH-291BT Head Unit (No Navigation)**
Alright, long story short I'm a cheapo and didn't want to spend money on a micro bypass switch or a switch in general. I wanted to use what I already had. Researching online I found that Pioneer updated the Parking Brake ground out work around and now required a double signal. Here goes a picture of the pattern they require.
We need a switch to send a On, Off, On signal. Thinking about what I already had, I figured I use the headlamp switch. You need a switch that you can vary the voltage through... the dimmer wheel!
I didn't circle it or highlight in the picture, but the wire you want to use is #2 - Panel Lamps Dimmer Signal.
I don't have a video because it was dark and cold AF outside but the Pioneer pattern screen pop up appears again. All you need to do is have the dimmer switch set to the MIDDLE setting w/the cargo light coming on when you open the door (not always ON), turn it down till the warning screen comes on, rotate it up (again, not always ON) and hit "OK" when the pop appears again.
Unfortunately, you will have to put up with the dash, A/C controls, etc... always being on the "BRIGHT" setting. You can put it to the "DIM" setting but you will not be able to watch movies while it's in this setting.
Now you can... I mean your passengers can watch DVD's while your automobile is in drive!