Further, according to FDA, a “general wellness product” falls into one of two categories, and either:

Has (1) an intended use that relates to a maintaining or encouraging a general state of health or a healthy activity, or (2) an intended use claim that associates the role of healthy lifestyle with helping to reduce the risk or impact of certain chronic diseases or conditions and where it is well understood and accepted that healthy lifestyle choices may play an important role in health outcomes for the disease or condition.

FDA explains that to fall within the first category, the product must not make any reference to diseases or conditions.
FDA provides a number of illustrative examples of products it would consider to be low risk general wellness products, including mobile medical apps that:
– Play music to “soothe and relax” an individual and to “manage stress”
– Solely monitor and record daily energy expenditure and cardiovascular workout activities to “allow awareness of one’s exercise activities to improve or maintain good cardiovascular health”
– Monitor and record food consumption to “manage dietary activity for weight management and alert the user, healthcare provider, or family member of unhealthy dietary activity.”
So, I agree that fitbit with no impact on any disease.
https://www.fda.gov/downloads/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm429674.pdf