Frank,
Yes, you can track the invitations a user has sent. The tracking of who has sent and invite and who they have sent to is automatic and happens even if the user hasn't approved/logged into your site. You can track if the receiving user accepts them *if* they login to your app. Facebook doesn't allow you to know if a user has accepted a request if they don't accept/approve/login to your app first as that could be an information disclosure (privacy violation).
For a demo of the invitation feature, you can try it out on our demo site:
demo.sourcecoast.com/index.php?option=co...icle&id=4&Itemid=154
Once sent, you can see how it looks in the admin area:
demo.sourcecoast.com/administrator/index...=display&requestid=1
You can even customize the Request if you'd like in the admin area:
demo.sourcecoast.com/administrator/index...uest&task=edit&cid=1
Hope that helps explain, but if there's something else you were looking for, just let us know!
Alex