In order to monitor internal resources of remote systems with Nagios you will need NRPE installed and configured on a client. There will be two pieces to install NRPE daemon and nrpe plugins. This particular install was tested with CentOS and Debian.
Nagios is excellent monitoring tool and python is very powerful scripting language. Lets take a look how we can put this 2 together to create our own website monitoring plug-in. We will monitor basic public http response via python httplib module. In our example NAGIOS is installed on CentOS 7, procedure should be the same