Mobile app for fitness startup -- 2

I am looking for a mobile app developer to create an app for my fitness startup. The app should be developed for both iOS and Android platforms. I do not have a specific design or layout in mind, so I am looking for suggestions from the developer. The app should have the feature of tracking workouts and progress. In addition, integration with wearable fitness trackers would be a plus. I am also interested in offering in-app purchases for premium content. Ideal skills for this job include experience in mobile app development, UI/UX design, and integration with wearable technology.