I'm guessing this is the same video Trail JK mentioned. I was checking this out yesterday too.
https://www.youtube.com/watch?v=fHLNKOkpG4A
I'm surprised at all the Trail Dash can do. I thought it was just a calibration tool and for reading OBDII data, but it will let you control a lot of features on the fly too. I don't think they showed it in that video, but they also make wiring harnesses to let you control accessories like light bars, an air compressor, etc right through the touch screen on the Trail Dash. Pretty cool.
...Come to think of it, I wonder if you would be able to hook more than one camera to it. The way it's a modular accessory harness makes me think it might be possible, but you could probably only view one at a time.