I’m just guessing here.
But it could be possible to put the doorbell and camera system in its own network that’s only accessible via the local network. If you make a VPN to the local network, only the person with credentials could VPN into the camera network from outside.
I’m a noob at this though, so I’d need a guide.
Where are you that National Parks are so inaccessible for you?
I’m not doubting, I have no perspective on this because I’m from Calgary where I go to them on a near weekly basis and it’s cheaper to go to them than anywhere else.
Funny thing is, very few Calgarians get to go to these places not everyone has a car and options for transit to Banff and Waterton is extremely limiting. It’s definitely a middle/upper class thing