Looking to fit a dash cam which has a separate rear cam wired to the front one. Is it any more involved than removing the trim from the end of the headliner, and the trim around the top brake light, to feed a wire through the rubber thingy? 

Edited 8 July, 20196 yr by anewman

Not much more than that for a simple rear cam. For a reversing cam you would additionaly need to pick up on the reversing light feed and an earth, simplest in the boot at the lights.