User approved references?

Hi,

I'm sorry if this has been asked/answered before, but I can't seem to find this information.

I was wondering if anyone knows of any contrib module that uses ER that would allow a user-reference to require approval.

So, if User A wants to set User B as a reference, could that be configured so User B has to approve? I see this is what http://drupal.org/project/user_relationships offers, but I wonder if there isn't something more geared toward entities and entity references rather than users...

thanks