Hey,
I run a dash cam on both of my vehicles. I use an ION 3 wifi, it records when I flip the switch on, and is not powered by the car, I charge it every 2 days and have a 64g micro sd card, I erase the footage of nothing happens, as far as the rear of my car, I have an innovv C1 that is plugged into my cigarette port and records when I turn on my car (be careful as some cars have an always on cig port) the IOn 3 also clicks off easily and I have it placed on the handle bar mount on my motorcycle when I ride it to cover the front. For the rear of my bike I am currently unprotected but I have a company making a custom little plastic box so I can run it on the rear and not get it wet or risk it getting stolen, I should get it Wednesday. I custom made an ignition on circuit for the motorcycle to charge a USB power bank I tied into the bike and made waterproof, ballin LOL! The IOn 3 was about 250 from best buy and the innovv was about $50 a piece, the cool thing about the innovv is it has a built in battery and can keep recording if you are involved in an accident which knocks out your electrical system, this also allows you to set a 5 or 10 minute limit in which it keeps recording after you turn off the ignition, which is good because if you are away and someone hits or keys your car, you are covered. I haven't activated the setting as I am always busy haha! If you want send me a private message and I'll text you picks of the setup, or one day if I am not busy I can meet up with you and show it on both vehicals. Hope this helps.