However, you are using a PAM module that was developed by Google. I'm not sure if Google's Authenticator program has enough of an API to allow any program to implement 2-factor authentication using their program yet, but it could be possible.
Good to see it can be implemented outside of Google products.
Edit: of course, this is just another implementation of the TOTP method. It does not use Google's infrastructure to send you SMS / voice calls containing the code.