My installation cost $0.00. This post was very helpful:
https://g30.bimmerpost.com/forums/sh....php?t=1457675
I know that my wires will not interfere with the air bags. The wires to the rear camera are under the floor trim.
I'm using an external battery for my Blackvue DR750S-2ch which is located in the glove box. Out of sight, but well-ventilated and easy to access.