What a terrible question to ask. I was planning to wire it directly to constant 12V, but after your question, I'm second guessing myself.
I started thinking that the ultimate solution would be connecting it to an external battery pack that is recharged by a Tesla switchable 12v supply. That way battery drain would be minimized and the external pack could keep the blackvue powered for a few days.
Argh. What have you done (or planning to do)?
Sorry for asking... ): I wired directly to the car, the installer wired it directly to a always on power source under the carpet on the drivers side. I believe you can also use the OBD port for power as well. You shouldn't have any battery drain issues since the Tesla always replenishes the 12V battery from the main pack and the dashcam uses very little power.
This is the new battery pack: BlackVue B-112 Power Magic Battery Pack
It is also on Amazon but not from an authorize seller currently: http://amzn.to/2c93rju
I will look around for more places.