Nagios-plugin for retrieving data
http://mathias-kettner.de/checkmk_index.html

Check_mk adopts a new a approach for collecting data
from operating systems and network components. It
obsoletes NRPE, check_by_ssh, NSClient and
check_snmp. It has many benefits, the most important
of which are:

* Significant reduction of CPU usage on the Nagios
* host.
* Automatic inventory of items to be checked on
* hosts.