title: Sending a response after app starting from a intent-filter
body: <p>I'm trying to implement the PICK and SET_WALLPAPER intent-filter, and so far I've got them in the context menu, but how do I respond back to whoever started the app that way? Lets say I have the activity:</p>
  
  <pre><code>&lt;activity
      android:name="ListActivity"
      android:label="@string/app_name" &gt;
      &lt;intent-filter&gt;
          &lt;action android:name="android.intent.action.SET_WALLPAPER" /&gt;
  
          &lt;category android:name="android.intent.category.DEFAULT" /&gt;
      &lt;/intent-filter&gt;
  &lt;/activity&gt;
  </code></pre>
  
  <p>When this activity is successfully running, and I know what image (I know it's location on external storage, and could have a Bitmap of it), how do I send this response back so that the app that started my app can use the response? I'm thinking finish(), but what extras do I then add? Does this come down to the specific app that started my app? Thank you.</p>