I have two examples of Intentservice. One is the Download example in the commonsware book. the other is at http://www.vogella.com/articles/AndroidServices/article.html#ser
To keep a service running, your service need to return START_STICKY in the service method onStartCommand().
With this, the service will be running even if you exit form your activity.
Note:
The Android still kills services after some time (30 mintus to 1 hour) if they are not foreground services. Use startForeground(notification) to make it foreground.
good luck