authenticate google apps via wordpress login

I would like to to use an internal staff blog at my organization to be the gateway for google apps that I’ve set up under our org’s domain. Has anyone come across a plugin that would automatically authenticate google apps when users authenticate as wordpress users?

I’ve been experimenting with app gateway at gnucitizen.org:

https://www.gnucitizen.org/blog/gnucitizen-wordpress-plugins/

But a) I have not yet succeeded in following the directions for adding new applications and b) I’m not sure the app gateway is practical for setting this up for 30-40 employees.