I added a new sample, minimalistAuth.xml that uses the Standalone Auth Client. It loads slightly less JS on startup, but cannot make use of the full Google JS Client API. Thus, the example only retrieves the access token and doesn't make any further calls.
This can be a little lighter-weight if you are only using your access token for verification---that is, you're using it to tell that the request came from a particular user, rather than using the token to retrieve new data.
I also took the liberty of updating the old experiments to use v1.1 of the hangouts.js library.