When certain programs run, they add indicators to the Launcher. For example, Update Manager adds the number of items and a tiny graph indicate its progress. An example is shown in the attached screen-shot (Update Manager has 8 items, and it has nearly finished installing them).

What I want to know is how to add them myself from a script. For example, if I am using yad (a Zenity fork), how can I overlay the yad icon with these items?

Related to this, how can I change the actual icon being shown?