Plugin to another android application

I'm new to android pr开发者_StackOverflowogramming.

Does anyone know how to listen for actions that other applications do?

You need to be specific. You're probably thinking about BroadcastReceiver (look it up in the SDK). Also, apps talk to each other using intents (there's also a big section about intents in the dev guide itself). You can add menu options to other apps IF they use addIntentOptions. Again, if you want a more specific answer, you need to be more specific in your question.