Hi, I've developed a very simple (I'm not an expert) statistics module. I tried to upload it here but the forum let upload 100 Kb max. (the library to create the graphs is 3 MB).
Just unzip the files and add them to your installation (make some test first, don't blame me if something is wrong).
http://www.gigasize.com/get/2g0qzzfxvhc
If some one can make it better, please share it. As I said, I'm not an expert, but if you need it, use it ;)
