Sign on with google apps account only

Hi,

I’m intending on using a wordpress website with buddypress/bbpress + some other plugins to create an intranet for my small organisation. I’m looking to have my users register and sign on with their google apps account.

I’m considering using a social login plugin, but the problem is that I don’t really want to even offer the option to users of choosing among Facebook, Twitter, Google etc. I wanted a simple username/password box or a “login in with google” button that only accepted @organisation.org accounts and not the general public.

Any one know of a plug in that will allow this?