I just did the install on my 2017 Model S. Here are a few notes and pictures from my install.
PLEASE NOTE: Watch the video that was posted by BigTonyTones first or else this wont make any sense to you.
1. I used the "fan cable" and plugged right into the unused connector in the microphone grill. I then ran the cable out from the corner of the grill before snapping the grill back in. I did not want to mess with the 3 forward facing camera housing so I just used the small little sticky cable holder and stuck it on the right side of the camera housing and then ran the cable to there and then to the blackvue. It sits nice and flush and you can hardly tell its there.
2. I ran the cable for the rear camera up and along the headliner and windshield. I used the blue pry tool that came with the camera to pull the headliner down from the windshield as I pushed the cable up into it. Very easy to do. Don't forget to route the cable on top of the air bag once you come to the door molding. I then did as instructed in the video and ran it under the molding.
3. Once you get to the rear hatch seam right behind the little window in the backseat passenger side window area, you can pry off that panel but do it AFTER you remove the Shelf bracket in the trunk. I then brought the cable back on top of the rear airbag and used a long zip tie to fish the wire from where the boot was removed that holds all the existing wiring.
Below you can see how I removed the shelf and the side panel. The panel and shelf both pull straight out and away from the body. Not up.
I removed this panel while I was sitting in the back seat of the car(on top of the folded down seat). You can see how the clips are on the panel - pull it straight out towards you.
You can see part of the airbag in the picture below. I made sure the cable was routed on top of the airbag.
This is a picture of the zip tie that I pushed through the bottom boot into the cabin
Picture of the zip tie poking through to the cabin.
I then routed the wire through the rubber boots and then fished the zip tie from the top boot and it popped out where you can see the wire hanging on the top left of this picture. I did cut off the plastic tip of the wire, but after further inspection, I think I could have tried fishing the wire through with the tip on. If that doesn't work, you could take a razor and then just cut straight down the plastic covering on the gold connector then try fishing it through. I regret cutting the wire before I even tried fishing it through the metal window hatch.
Now i'm waiting on the new connector to put on the wire before connecting it to the camera. All in all, it was a pretty straightforward install. I hope the pictures help someone in the future.