I know this has been discussed on the teslamotors.com forums, but I thought I would add my experience here. I installed an iTronics ITB-100HD dash cam in my S, and it took all of about 30 minutes (plus an additional 30 minutes driving in the ICE to go to the auto parts store and buy a fuse holder :crying
. I, as many have now done, also tapped in to the unused 12V connector under the microphone screen, but I also routed the cable under the headliner/rearview mirror plastic housing. Pictures and description of install follow thusly:
I didn't have any fancy male plug to use with the existing connector, but I found that if you pop the two small retaining clips on either side of the connector, it opens up to allow access to the metal leads. I simply laid my stripped wires on top of these leads and snapped the connector cover closed. A significant tug could not dislodge the wires from the connector, so I am confident this will suffice.
I routed the camera power cable thru the headliner and under the plastic housing for the rear view mirror. The plastic housing is held in place by the windshield moisture sensor. If you slide a plastic pry tool between the windshield and the housing, and bit of light pressure should get it to pop off the sensor. I ended up taking off the entire rear view mirror, but I think that was overkill.
Once the housing is "loose", there should be enough wiggle room to worm the power cable from the power source thru the headliner and under the housing.
If there's not enough room and you need to remove the housing, you can "split" it by gently prying it open. Be very careful! Some of the clips really did not want to come free, and I nearly broke one of them off. There are five clips that hold the two halves together. The picture here is the right half of the housing. For orientation, the bit that's closest to my ring finger is the part where the mirror goes.
I then just snapped it all back in to place. There was enough play in the fit of the housing that after everything was put back in place, I was still able to tug on either side of the power cable and get it to slide back and forth, making the final fit very easy. From the outside, you can barely notice the camera. From the drive seat, you can't see it at all, and from the passenger seat, you can barely see it. Pretty happy with the results! Thanks to several people on the forums here who inspired me to do this myself instead of paying my local car hacker $350 to do it for me!
Interior:
Driver side:
Pax Side:
Exterior: