http://www.computec.ch/projekte/browserrecon/

browserrecon is an open-source suite which was developed for passive web browser fingerprinting. The basic idea is that the scripts are running in the background of a given web application to gather the implementation details by the clients. This process is not depending on the User-Agent information, which might be forged, only.

The current release of browserrecon is written in PHP. Therefore, you might be able to use browserrecon on a web server supporting PHP. If you want to include browserrecon in a given web application, the software has to support PHP itself or a fork of the PHP scripts.
i will test it and report, but it seems to be realy interesting.