Workout Timer: HIIT Interval is an interval training app for iPhone, iPad, Apple Watch, and Apple TV. It provides timers for workouts such as Tabata, HIIT, boxing, AMRAP, and core training, with configurable work and rest periods. The app includes studio recorded voice coaching, seven guided video programs, and a large countdown display for use in a home or gym. During guided sessions, video demonstrations show exercises during work intervals, while previews identify the next exercise during rest periods. Programs cover core and abdominal training, strength, full body cardio, and other conditioning routines. The app also supports Apple Watch and AirPods heart rate display, and includes Apple TV features such as a split screen coaching view, Siri Remote navigation, and a 4K countdown display designed for viewing across a room. The typical workflow is to select a timer format or guided program, start the session, and follow the countdown, voice cues, and exercise demonstrations through alternating work and rest intervals. The app’s website describes it as supporting offline use and identifies tvOS 17 or later as the requirement for its Apple TV features.