This app allows you to track your high intensity interval training workouts, without getting in your way. You can have vocal cues that guide you through your workout, or use the timer interface to know which exercise to do, how long to do it for, and what to do next. You can also create custom workouts and exercises, and control the timing of your exercises and rests. The workouts are structured to be high intensity interval workouts, but you can create your workouts to suite any type of workout you want to create. This app uses HealthKit to give you more insight into you workout. The data is not sent anywhere, and stays on your device.