I see all you pilots have individual opinions but, as a QM in several UK companies, I've had to deal with several GoPro cameras mounted in a variety of rotorcraft for Reality TV purposes.
One enterprise fitted four cameras to one of our Helis before informing the company (the pilot just let them modify the aircraft while it was on-line - but what do pilots know about aircraft maintenance?)
When the cameras were reported at the head office they were all immediately removed.
The TV producers (who the Pilot let crawl all over his cockpit?) had fitted them around a cockpit/cabin all linked to a single battery to extend their cameras lives over a full shift - this breached Dangerous Goods rules by the size of the central LiPo battery and they had to provide a detachable pouch in case of battery overheat.
'They' also routed camera power cables around crew door frames where they could cause foot or neck entrapment - again, in breach or door clearance regs.
Another enterprise at another company tried to install home-made bracketry to the frames/fixtures - and this constituted both an unapproved mod and a permanent fixture. The camera team had to get their bracket, and where they wanted to mount it, approved as an STC before they could install it.
As for mounting on the outside using only the device for mounting on a car! Well, I'm not really surprised at some of the unqualified speculation here...