I drive primarily at night, so I needed a good setup.
After trying a couple mid-level dash cams and having no luck with night vision, I figured I'd think outside the box a little. I don't want to spend a lot and even the high end models I thought delivered questionable night vision considering the price.
I had an SJCam GoPro knockoff sitting around that I use on my motorcycle endeavors, so I was already aware it was a good dash cam option for cheap, with reasonably good low-light capabilities for front-facing duties. It didn't work well facing the interior tho, with little illumination. So, I went about fixing that. So, know up front this method requires a little tinkering, some basic hand tools and a tiny bit of risk. If you'd rather just buy a plug-play solution, awesome, but this is for the tinkerer who wants a good way without breaking his/her wallet.
For this setup, you'll need (2) SJ4000 or SJ5000 cams. Makes no diff which, either works fine for this role. The important thing to know is that there are a bunch of knock-offs out there, and model you need for the interior cam MUST have the HDMI-out port (I'll get to that). The front facing model doesn't need this, you can buy whatever. These cameras start at $17 on ebay....just be sure at least one of them has the HDMI out.
Here is an example of the exact model I refer to. https://www.amazon.com/dp/B01GPXRDS2/?tag=ubne0c-20
The non-hdmi versions are cheap and plentiful, so buy whatever there. They all seem to have similarly good video quality.
Once you have that camera, you'll want to remove the IR filter which will allow it to see in full spectrum and catch infrared illumination for the interior of your car. This is actually quite easy, several youtube how-to's cover this. This shows you how to remove the filter, how to re-focus the lens (where the HDMI comes in), and also the exact configuration of the SJcam you'll need. If it has HDMI, it has the IR filter (some don't have an accessible filter). You'll need 2 microSD cards as these cams do not come with them. MicroCenter or Frye's has them silly cheap. It may look involved, but it was really really easy.
So, once you've gotten here, you have two high-res, good low-light cameras you can use to capture forward and interior/back, and both models come with mounts...but if you want more mount options, again ebay sells every kind of Go-Pro (same as SJcam's) mount known to man, cheap. These cameras can be powered by readily available micro USB cables (same as an android), so that's easy too.
The last thing you'll need is an IR illuminator for your interior. You can buy 12v models on ebay or Amazon that are plug and play, but I found a cheaper option. For about $11 you can buy one that's 12v but does not have a cigarette adapter with it, and if you're handy with strippers & a crimper, you can add a plug to it easily (I had one laying around from an old vacuum, so that was a no-brainer). This model puts out a lot of light, and is perfect sized to sit in a cup holder or on your dash.
So, if you bought all this as cheap as possible without having some of the stuff laying around like I did, you're looking at about $100 total for 2 cams, mounts, cables, lights, IR illuminator and storage. You can spend more, or you could spend half that if you have some stuff laying around or you ONLY want to make an interior cam. Totally up to you how you roll, but the other benefit of this set up is you can pull these cams and use them outside the car for fun or whatever....they're useful little action cams, so they do great double duty.
So, the big question is, how well do they work? Well, pretty darned good IMHO. I'm still playing with positioning the IR light and settings (I only had one full night of Uber so far, so I haven't fully explored the options yet), and the cameras have their own light settings which I haven't delved into, but just a cursory test was good enough to accurately document what happens in front and in the car. I just pointed the IR light up at the dome light to bounce it off the headliner and diffuse the light a bit. The area we're driving through is pretty dark, normal camera on this same road was just black trying to film the interior to give you an idea.
Like a moron, I used the waterproof mounts on this first test, not realizing they muffle the sound a LOT, so the audio sucked....if you use the normal mounts, audio is great but this footage is mainly to show the video quality. I'll upload a new vid this weekend after I do some more testing with better audio, but trust me you can hear your pax just fine.
And yes, my drunk pax took my hat and I totally let her because she had nice legs. lol. Got a nice tip for that ride, so fellas always share your hat.
Anyway, just thought I'd throw this out there as an option for folks wanting a dash setup.