title: activity sending data even if user has exited it
body: <p>I want in my app to do the following. I wan even if the user press the home key my app will still continue to send data (indefinitely until the app is killed). In pseudocode I want something like this:</p>
  
  <pre><code>even_if_i_have_pressed_home_button {
      for (;;) sendData();
  }
  </code></pre>
  
  <p>Can you help me in what to use? I have read about services, threads or runnables. Can you suggest me something and give me example code?</p>