Minicounter_XH facilitates counting the visitors of your website. It's a very minimalistic counter, that will only count the total number of visitors, but this could be implemented in a very efficient manner by storing the required information temporarily in a PHP session.
It requires a UTF-8 encoded CMSimple_XH installation and PHP ≥ 5. It is released under GPLv3.
There is also a beta version available, which is supposed to be compatible with CMSimple_XH 1.7: