Finally, my Firefox Add-On has been submitted to the gallery and awaits its review.
Since I found the Icinga Status Add-On for Google Chrome I wonder why there is no such fine piece of software for Firefox. I used the Nagios checker, but it does not work with Firefox since Version 29 (no status bar there) and missed that little neat feature to reschedule a service check.
So go grab it and test it. Feedback is welcome!
Firefox Add-on page: https://addons.mozilla.org/de/firefox/addon/imoin/
GitHub repository: https://github.com/ErikWegner/imoin
Btw, imoin stands for I MOnitor Icinga or Nagios.