The Apple Watch is an excellent tool for working out. Using the native Workout app, you can record and monitor a whole range of different workouts, from running and cycling to skipping and yoga. If interval training is your thing, there's also a HIIT option, that includes a range of interval options, such as 10 minutes of 40 seconds work/20 seconds recovery, or 20 minutes of 45 seconds work/45 seconds recovery.