Which device do you need? Depends on what you want to collect. Check the specs below.
Generally, if you want unobtrusive background data collection, we recommend the Garmin's vivosmart 4 (least obtrusive, cheapest) or Venu SQ (entry-level but has all the sensors). Buy through us for a discount.
If you are not sure what to pick, send us a message at support@physioq.org