Integrated into iOS 5, Message+ allows you to reply quickly to your incoming messages (SMS and iMessage). Messages+ even allows you to dismiss the SMS/iMessage banner at your leisure and groups message alerts together so that you have the most up to date message displayed. You can compose a new message using activator actions (by default, swipe your finger from the bottom of the screen).
Messages+ – SMS the way it should be.
Note: Messages+ is integrated into and included (for free) in IntelliScreenX