I hear ya. I just needed to do a little digging.
I ended up collecting the data I wanted via a JS function, then, at unLoad or window.close, putting those variables in to a form and using form.submit() to automatically send the form to the appropriate .php script on my server. Of course, the variables were method="post" through the url.
The down side is that everyone can view/source and see the client-side JS. Not to be selfish, but it is a small part of a commercial service.
Thanks though 🙂