cocoa touch - Dynamic iPhone App icons?

Question

The calender app does it... How can I make an app icon change based on stored info from the iPod or iPod app settings?

EDIT: I realized today that it is possible to access bundles via the sdk. (At least read access) If I had a graphics API (OpenGL, perhaps) then I could possibly modify the icon like that. The operation would be:

• get icon.png from bundle.
• modify it
• resave it into the bundle.

Does that make sense?

Answer 1

Just as a note, Apple's Calendar app is actually hardcoded into the system to display a view over the icon. Put it on the left of the first page and drag to SpotLight, you will notice that the text fades out differently.