There's not, but what kind of interface would you need?
I could easily extend the existing API. That would provide a good separation from my addon if you're planning on sharing it.
Could easily shove a function for you to call in one of the libs modules.
Or could use a property on the home window, but this wouldn't check to see the connection was still alive before reporting it (which may not be necessary if this is happening frequently enough via the service)
Whatever the VPN info dialog calls to display the DNS and IP address can you use the same call for skin someway?
I don't know much about APIs unfortunately only know about skinning.
A home property or function would be good to test.