Access the info about my installed applications, files, and contacts?

Hello
I’m currently working on an augmented reality application on my android phone. I want to make some sort of app manager.

Is there any way I can access the info about my installed applications, files, and contacts?
Thank you in advance.

Check out http://unity3d.com/support/documentation/Manual/PluginsForAndroid.html. You could write a plugin to pull that information from Java code.