Is it possible to detect when an app is executed (i.e., when the user clicks on the app's icon)? I attempted to register an intent of type `Intent.ACTION_MAIN` using a category of of type `Intent.CATEGORY_LAUNCHER` hoping this would let me know whenever an app is launched. The problem is, my broadcast receiver is never getting called. 

Is this an illegal intent/category combination for which to register? Is there some method I can use to determine when an application launch occurs?