Ok, so I'm thinking about installing Prestigio Roadrunner 500 or similar car cam, but the only thing that's bugging me for now is how to neatly hide the cables and make the camera not so prominent (doesn't have to be 100% invisible)?
if you mount the camera next to the rearview mirror run the cable in to the roof lining, down the A pillar and behind the dash. I personally would wire a new 12v socket out of sight behind the dash that is powered by an ignition live so that the camera comes on with the ignition.
I do not know of any how-to's for this. It is very simple though. The wire will easily tuck in behind the roof lining and the trim of the A pillar then down behind the dash. Hopefully someone else can tell you where to find the easiest ignition live feed
As for running the cable, it will be pretty straight forward as MollyGoogle said. You can literally just tuck the cable above the roof lining trim and along the a-pillar. If you need to actually remove the a-pillar trim, then it just pulls off.