I wrote a module some time ago that pulled MongoDB-stats via the mongostat-command and collected this to Observium. I attached my patch for the mongodb-agent here, it should help you do a similar thing for your application.
A short explanation of the files:
scripts/agent-local/mongodb - this is the script that runs on the host with mongodb that you want to monitor, Observiums unix-agent will execute this script and the output will be put in the Observium-database
includes/definitions/rrdtypes.inc.php - here you put the definition of the RRD-file for your new application data
includes/polling/applications/mongodb.inc.php -
This code takes the data from the Observium-database and sort it the
way you want and then creates RRD-files with all your values
html/pages/device/apps/mongodb.inc.php - this files defines how your different graphs should be sorted in the webpage
the rest of the files named like this:
html/includes/graphs/application/<app>_<category>.inc.php
are
just definitions of what data should be pulled from the RRD-file for
this category/graph and how to color the different values.
The page will then be displayed as the image attached.
Other than that you only need to apply some small png-images for icons and then you are done.
Hopefully this help and the page http://docs.observium.org/developing/add_app/ should give you enough information to add your application to Observium :)
/Markus