I need to run a timer in the background for all activities. Sometimes the timer will start a new activity briefly. Then the user can close that new activity. What is the simplest way to do this? If I start the timer on the first activity will it run through all other activities? I'd rather not use a separate service. If a service is the best way, can I create the service inside my current app? I don't want it to run outside my app. Thanks!