You would need to make a plugin to listen for a socket event, and in the widget js send the needed data to verify the request server-side. After adjusting the reputation and sending the new rep back, you probably want to make a db key to record the last action taken, such as how core uses pid:x:upvote
@kenygamer I'm far from a developer. The folks at firstname.lastname@example.org are probably the best bet for a customer plugin. It sounds like you don't want to use single sign on (which relies on cookies or session tokens), you want to use a full on external database for authentication.
I think from a user experience, cost, and level of effort; you'd be better just having the users register on the forums.