For a detailed description see http://kde-look.org/content/show.php/Service+Monitor?content=125203

Simply run the following command:

$ plasmapkg -i /path/to/service-monitor

then add the widget in KDE. If you want to remove it again, run

$ plasmapkg -r service-monitor

For development, you can use plasmoidviewer to quickly start the widget from command line. This way you don't have to install/uninstall all the time.

Please note: the master branch may contain a temporarily broken version; switch to a release branch for a working version.