I was not happy to find the Fitbit only works by syncing through their service - eg they get all of your data, and vigorously opposed requests to just link to HealthKit and not upload data.

Now it seems they were deliberately making sure they had your data so they could (in effect) sell it.

I’ve held off on an Apple Watch for the longest time due to battery life and size, but it seems like that is now the only option. You can’t trust any company to have access to your data.