I'm currently thinking about buying a fitness tracker, and this article definitely rules out a Fitbit.
Does anyone know a fitness tracker that does not share my personal health data with anyone?
Apple Watch? There's a heart study you can participate in by sending your heart data, but it's opt in (and you have o be 23). If you don't have an iPhone I'm sure there are a couple heart rate trackers that don't upload to the cloud, but you may have to drop down to a "dumb" device to ensure this.