WatchFit and its developer take your privacy very seriously. WatchFit itself does not store nor transmit any personally identifiable data.
In-app purchases are processed in an anonymous way using RevenueCat. You can access their privacy policy here.
WatchFit uses no analytics and collects no personal information. All processing is done on device and data is stored and synced on the user's personnal iCloud account. The developper does not have, in any way, access to the data stored on the user's iCloud.