Thanks Technic for your review
The BimmerTech rear view camera solution for the 3-series is the best one on the market
The OEM option mentioned above is not a dedicated 3-series solution.
Since parts come from other BMW model you need to cut the trunk lid to fit the camera and installation is definitely not PnP.
If someone if interested in doing it this way to gain the guide lines and obstacles marking we would be happy to offer it.