th3magpi3 just completed this in addition to Android Auto retrofit, video in motion and the regular vin programming in my 2015 Sierra. When driving and pushing the rear camera icon button, it will pull up the video with a 25 second timer. After 25 seconds it will go back to the home screen. When in Park there was no time limit.
The harness that was provided for the rear camera was very good quality and looked like it was OEM, and super easy to locate the connections.
I briefly tested out the video in motion and it worked once I formatted my USB HDD to NTFS. It recognized MP4 and M4V files, but not TS files from my home DVR, which I kind of expected. I hadn't played with the video features prior to to having VIM enabled so the formats it plays may be common knowledgeto others?
Everything is working great and Chads support was fantastic. I saw a couple minor issues after the install, which I came to find out were perfectly normal and corrected themselves with a few power cycles
I'll post a video of it hopefully in the next day or 2.