I'm looking into the Planet Halo ph4 multi channel kit. I think it constantly is on and looping or at least can be programmed to do so. Haven't priced it yet but living in Portland, theft is always a concern. The vehicles can can be accessed from the internet, gps located, and can be used in many different views both inside and outside the vehicle.
Remote viewing is going to cost you a pretty penny....plus all the subscription crap.
You may also consider the DVR-50 by Echomaster; 4 channel DVR with remote trigger inputs if you buy the DVR-50TH harness.
Once triggered - the DVR should automatically turn on and record camera inputs. I'd recommend cameras with IR