How do I launch the app on my iPhone?

Once you configure the app you just need to put it in the background by pressing the iPhone home button from the LifeSaver home (blue) screen. Then leave the app in your background task list.

You shouldn’t need to open the app each time you drive, it will detect driving and score. If the app dies for some reason, that would be one reason to click in the app to open and place it back in the background.