Just found this at http://blogs.zdnet.com/Google/?p=109

The Trusted Tester Program gives the friends and family members of Google employees a chance to test early Google confidential betas and let us know what they think. To become a Trusted Tester, you first must be invited by a friend or family member who currently works at Google. You can then log on to the Trusted Tester website with a Google Account in order to access and test out betas of new Google products as they become available.

cheers
viggen