Advanced Javascript developer required

I am in process of building an analytics service in php and need a javascript developer who can help me build the javascript part of the site. You would work on a code snippet which i can give to my clients to embed on their site. The code would be able to insert a cookie on a visitors computer, know if we have inserted a cookie before, relay some data back to my site, detect events on the website page such as: Click of a button, visiting a url or submitting a form. The code would be able to relay this information back to my site using URL rewriting to translate the requests for .img files to .php files on the server side.

If you have heard about/used kissmetrics, mixpanel their code is similar to what i want to accomplish.

I understand that this is quite advanced stuff but i need someone who can do quickly and do it well. I can give a proper explanation if you don't understand my needs, just send me a message. If you have worked on this sort of thing in the past, that would be a plus.