im working on doing server load (if that is what you mean). I'm sure there are some extensions or built-in PHP functions for it. I usually create my own code by looking at other people's code (especially if its GPL), i read a few copies, then i create my own version with the best of all the ones that i read about.
EDIT: Load info is almost impossible to implement. I've looked at the most popular application, phpSysInfo, examined their source, tested on Windows XP as well as Linux. It completely fails on XP, and in Linux, since we are on webhosts, theyt would have some restrictions on which files we can access. My host did not let me read the file with the statistics, and got this error:
PHP wrote:
open_basedir restriction in effect. File(/proc/loadavg) is not within the allowed path(s)
Thus, i have concluded that it is almost imkpossible to actually get this statistic to work, even in future versions.
phpBB 3.0 'Olympus' maybe allow you to access it because phpBB has its own dedicated server?

I'm not too sure, but most hosts will not let you read the priocessor statistics file for security reasons.