Adagios is a Web-based Nagios configuration interface built to be simple and intuitive in design, exposing less of the clutter under the hood of Nagios. It has a REST interface for both status and configuration data as well a feature complete status interface that can be used as an alternative to the Nagios Web interface.
openpom is a Web interface based on NDO for Nagios or Icinga. It allows you to view almost everything about Nagios or Icinga in a single page: alert, ack, downtime, comment. You can also interact with Nagios or Icinga through ack, downtime, comment, disable, and reset buttons. You can filter on hosts and services states (such as critical, warning, unknown, ok, or outage). The status popin allows you to display graphs, either the ones from Nagios (trends.cgi) or custom ones based on RRD (such as pnp4nagios).
NConf is a Web tool for configuring the Nagios monitoring software. It differs from similar tools by offering enterprise-class features like templates, dependencies, and the ability to configure a large-scale, distributed Nagios server topology. It lets you effortlessly maintain a distributed Nagios topology. It has a user-friendly GUI. It features host and service templates, a graphical dependency viewer, multiple authentication modes, a Nagios configuration importer, a CSV file importer, and a Perl database API. The data schema is customizable and expandable.
Nagios 4 iPhone is a Nagios interface for the iPhone. It does not require any modifications on your Nagios servers. The server part of this software collects statistics on several Nagios servers, serves a few static files, and generates a JSON response. The client part handles the display of the data on the iPhone.