It seems that in general support for this is pretty rubbish across Linux in general. Found some proposals for support in NetworkManager but nothing I can see in my distro (Arch) repos.

One thing I'm not sure about is how to handle automatic disconnection periods. IIRC fon/openzone logs out after 15 minutes of inactivity. As a result every now and then we will have to check the status BUT networks can allocate minutes or data restrictions, so we don't want to be checking unnecessary .