What's Sysmon ?
Sysmon is a tool to monitorise the state of one or more computers. It's based on a daemon and a php script.
The first has to be runned in all boxes you need to check, the second calls the daemon and prints the state into a nice web frontend.

The sysmond functions can be easily expanded by writing modules.

Documentation
You can read the man page here.
Documentation to write modules here.

Screenshot and samples
shot1
shot2
sample page