Low battery disconnect circuit recommendation?

[HABBERDABBER]

I've had several instances of leaving an aftermarket back-up camera plugged in to the cigarette lighter outlet and although "off" it drained the battery completely.

Any recommendations on a gadget that discoonects a 12V battery when voltage drops below a threshold?

[Eggscape]

There are plenty on Amazon.ca

Here is simple one that you can select via dip switches what voltage you want it to turn off. It also has a manual switch as well if you wanted to hard wire it in.
If you are handy then there are ones that are half the price without an enclosure.

[HABBERDABBER]

Yes, I've seen what's available but I'm wondering if anyone has experience with a brand or model.