We only support Apple Health, Google Fit and Strava at this time. Some devices are not compatible to use as an external device and may skew the data. This is partly to do with how Apple Health syncs data from the external device. We do not have scope to control this on our end. Our team is working on upgrades to be more inclusive with external tracking devices to enhance the activity tracking feature.
For Apple Health to sync to data from the Apple Watch the user must "start" the workout on the Apple Watch. If the participant does not, Apple Health doesn't recognize this exercise as duration and will not sync the activity. Apple Health independently only tracks Steps/Walks/Running/Cycling/Running/Stairs Climbed.