Hi,
I wrote a nagios parser for wmflabs, it downloads instance list from labsconsole and using simple application it parses it and generate nagios configs, it's currently running periodicaly on nagios.wmflabs.org and thanks to that nagios is updated when you create a new instance, it parses the gerrit classes from nova and define services according to that, currently it knows only apache service, but I can of course insert more classes there. The source code is located in trunk/tools/nparser. Thanks to Ryan Lane for the semantic query in order to get a list.
If you would find any problem with the parser or source, feel free to fix it!