When I want to do admin stuff, I propose to send an coded email (eg. specific words in subject) that will cause the webcam server to:
send and email acknowledge the coded email and
initiate a VPN to my home server.
Why not just keep a VPN up the whole time? I'd recommend OpenVPN. If you need a box with a static IP to run the VPN server, you can get one extremely cheaply -- see the deals on lowendbox.com, or for a box in NZ I'd recommend itlab.co.nz. You can set up a VPN server such that you can connect in from your PC at home to access the other VPN clients connected to it.
I don't want to use a VPN because:
If I make a mistake on routing and my home network traffic leaks onto the VPN, my monthly 750MB mobile data allowance will be burned up in a short period of time.
The additional traffic produced by a VPN will eat into my data allowance
I am running an old Optiplex GX50 as a webcam server. It copes nicely now but doesn't need the extra processing overhead of a VPN.
The webcam server is fully automated and will only need admin access every few months. I am not transferring images to my home network.
SSH will do exactly what I am aiming to achieve. A VPN offers me no advantages.