I just installed 2 Garmin Mini 2 cams, front and back. They can sync and when you record it will overlay the rear image onto the front image. I have the front connected to the OBD-II Port with their constant power cable, so once I turn off the LC it will keep recording for a set time or if the car gets bumped. The power cable has 3 time setting switch and you can fine tweak it even more in the Garmin App. I've had these running for a couple years in my last truck and finally got around to installing them into the LC. I was T boned at a 4 way stop about a year ago and even though it didn't capture the crash on the side it showed the other driver running the stop sign since I had both front and back recording.
Garmin Mini 2
OBD II Power Cable
SanDisk SD Card
Amazon.com