Dual channel dashcam?
There is lots of room for cabling around the headlining, the pillar trims, the internals of the light/rain sensor/rear view mirror housing.
If you are going for a dashcam, just be aware that even the "best" are flaky when used in a continuous parking monitor mode. They have a tendency to overheat, especially as the main doings are usually encased in the front (primary) camera housing which is right on the windscreen getting warmed up from the sun.
I had a Blackvue 650 set-up and it was well on it's way to being fully buggered in 10 days due to running hot, and looking around it seems to be a common problem. I don't know why these dashcam makers don't have a box with the main electronics that can be tucked away somewhere cool, and 2 satellite cameras cabled into it that on their own would not generate much heat at all.