It helps to give the user a potentially high priority message, such as a new text message, voice mail or incoming phone call, either when the user gives the phone their attention, for example, by opening a flip phone or when running an application such as a game in the foreground.
Providing users with timely alerts, such as new messages, voicemails, or calls, can be particularly effective when they have the user's attention, whether it's by opening a mobile device or focusing on a game.