How to pass data both ways between different android applications?

Question

What\'s the easiest way to pass string variables from one application to another and also return values back? I have access to the source code of both apps, but

Answer 1

I have two apps that i pass data to/from.

App1...
Intent i = new Intent("com.xxx.yyy.MESSAGE");
Bundle b = new Bundle();
b.putString("AAA", getAAA());
i.putExtra("MyData", b);
startActivityForResult(i, "myProcess");

nothing fancy there...

App2...in onResume()...

 Intent i = getIntent();
 if (i != null && i.getAction().equals("com.xxx.yyy.MESSAGE") {
    ...get the data from the bundle
 }

note that the AndroidManifest.xml (for App2) has the following entries for one of the activities