I have adapted Oldiesmann's SMF embedding code into a bridge only method and now have full member syncing from SMF to G2, excluding group management, while adding only 1 line of code to a default SMF install.
The bridge works by logging in a user into G2 when they log in to SMF and creates the G2 account if it doesn't already exist.
I don't have a Admin interface built as it is almost too easy to use as it is.
I have also implemented the latest g2ic using into SMF so SMF users can easily post their photos to the forum.
I already have this working in a live site. Is anyone able or willing to do more testing before possibly making it public (depending on feedback)?