How to build pluggable apps for Android?

Question

How does one creates pluggable applications for android?
If you have used GoSMS Pro, you can see that themes can be installed separately and then be used to change the main applications appearance.
I wonder how can this be done?

Answer 1

Well, you can simply send a broadcast that is received by all plugins (make sure they have a signature based permission!)

You might want to have a look at How to release application plugin using Android Market?

Answer 2

Third party themes are supported by some apps, like ADW Launcher and GO Launcher. However, the process of making them differs from app to app. For this app, they have release a tool which you can learn about here. After you've made on you can publish it using the details in @Force's answer.