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If you mean exercise tracking I use my watch on the runs and swims and the bike computer on the bike. Imho they are better than everything smartphone apps offer and also, the apps are draining the phone batteries pretty hard. And I like to be able to call for help 4 hours into a bike ride.
I use MyFitnessPal for calorie tracking and the TrainingPeaks app to have a look at my training plan and past workouts.