I watched a fascinating talk a couple of years ago by a guy who learnt in detail how various cars' computer systems work and communicate, (mostly by studying them directly, and reading the chip info when he found out what they were), connected to them, and eventually could play racing/driving video games with his car i.e. with the steering wheel, pedals etc. I can't recall the name, but I'm sure that would be useful and answer most of your questions. Maybe someone on here will know the talk I mean. (Can't see it on googling 'hacking cars talk' videos 20mins+ .. but that finds some interesting stuff)

I am curious about this too.

One thing I've thought about is being able to turn on the rear view camera on my 2016 Honda Fit while I am driving forwards.

The data path is there, and you might think it is just a matter of hacking the software on the infotainment system, but it turns out that the rear camera only receives power when it is in reverse so you'd need to change the power connection to a different circuit at the very least.

What I'd really love to do is put on a camera on the driver's side mirror to match the one on the passenger side mirror.

Trivial hacking is probably unlikely. Vehicles generally use CAN bus, but whether or not the camera data is available on the bus... I have my doubts, but if it's there, that'd be pretty cool. My guess would be there's a dedicated image channel off the main bus--but that's just a guess. I'd be interested in knowing if it's on the general network. It is peer-to-peer so in theory it can be deterministic, so maybe it is.

Yes, it's definitely not running over CAN as CAN doesn't provide enough bandwidth for cameras. Usually the cameras are connected using LVDS or in newer cars, ethernet.

Lvds? I assume the camera is some feet from the processor. Can lvds really be usedthat far?

I don't know why not; IIRC FireWire was LVDS (4+m), and LVDS doesn't specify ("care about") distance, just loss between driver and receiver. I vaguely recall lossless transmissions between 10-30m, which is more than enough for a vehicle.

Thanks for the follow up!

I havea suggestion, but because I am building one (although have yet to buy the equipment:

Ubiquity wifi + LTE + Wifi Cam in the vehicle - with cloud based view - Basically with this setup, you can make your car cam a part of your home security setup.

https://unifi-video.ui.com/g3-flex

I am currently reverse-engineering my recent-model Honda vehicle's camera system. It is not fun. It is delicate (in terms of hardware AND software).

tl;dr: Just buy a cheap, high-rated $60-ish dollar dashcam off of Amazon.