Nagios - Asterisk monitoring

i am looking into implementing asterisk onto Nagios for monitoring purposes; currently i have few asterisk servers out there and want to combine all asterisk into a single nagio page for easy monitoring purposes. Nagios must be able to : define by username and display all asterisk server based on that username. for example: usernameA will display xxx.xxx.xxx.100 xxx.xxx.xxx.101 and UsernameB will display xxx.xxx.xxx.106 xxx.xxx.xxx.108 admin will be able to access all IPs xxx.xxx.xxx.100 xxx.xxx.xxx.101 xxx.xxx.xxx.106 xxx.xxx.xxx.108 majority of my system are Asterisk 1.4.21.2 based running on Ubuntu 8.04.4 LTS distro. i would need nagios to monitor the status of asterisk, check_asterisk_calls, check asterisk alive, check_asterisk_channels check_asterisk_peers, The project is, (a)To install a nagios server with all the requirement above. (b) to guide me as to how to add new asterisk IP in nagious server (c) to guide me and to install needed plugin onto each of my asterisk server.