My laptop runs openvpn as a daemon using key authentication connected to my home network. Thisis mainly so I can access my home network remotely, but it works the other way also, letting me in to my laptop when its not in front of me. Openvpn as a daemon can also be configured to reconnect when it detects that network configuration has changed, so it is completely, transparently portable between whatever network my laptop is on, as long as that network has internet access.

If I loose the laptop, I can just revoke the key it uses to connect.