A smartwatch does not qualify as a medical alert bracelet (MAB). A MAB is usually made of one single material, does not pose a glass/brittle breakage risk, and is metal-detectable. Plus they can also be worn around the neck (necklace version) or ankle if wearing a bracelet is a food or occupational safety hazard.
The smartwatch also does not qualify as a medical device. Section 201(h) of the FD&C Act give a broad definition; a medical device is “any instrument, machine, contrivance, implant, in vitro reagent that's intended to treat, cure, prevent, mitigate, diagnose disease in man”. However, the smartwatch device isn't manufactured with the intention to do any of that, and any health/wellness app itself likely has a disclaimer stating it is not to be used to "treat, cure, prevent, mitigate, or diagnose disease."
The only FDA-recognized smartwatch feature I know of related to monitoring heart health is the Samsung Galaxy Smartwatch with IHRN feature. And that device is only recognized with low-level FDA-clearance (affirmation that device is safe and effective), and does not have FDA-approval (approval after device meets required clinical testing).
On a personal note: I have 2 close family members with pacemaker devices, and while there is an app, they have described it as "basically useless." And in the decade since smartphones became a thing, no doctor has ever recommended they monitor their heart health with an app.
If the employee absolutely *must* wear the smartwatch, you could try moving them into a location where there is no raw material or exposed food. If that's not possible, consult with Human Resources regarding reasonable accommodation under ADA and figure out if you might need to take other actions.
