Implementing OpenID sign-in for a Plone site

I have a client that would like to be able to sign in using google, twitter, etc. (that is, OpenID)
has anyone used OpenID on Plone? Is your implementation different than described below? Any suggestions on the best implementation?

Here is my findigs:
I found these sites:

the first depends on you setting up account with rpx and sounds burdensome.
the second link shows a different implentation of the Plone openID

Have you looked at ?