Congratulations on the launch, and I wish you well, and hope it is of great use to thousands!
> existing FDA-cleared hardware Can you please link to this?
Or perhaps more to the point - the problem you mention in OP seems, as described, like it's already solved by Kardia, what was missing that you had to build?
Now, how do I also get your software that will work with this hardware?
> The 510(k) Clearance process is one of two ways by which a medical device manufacturer can obtain approval from the Food and Drug Administration, although legally, a device clearance under this section is not a true “approval.” 510(k) Clearance simply gives the company permission to market its product, based on comparison to a “predicate” [previously approved] device.[1]
Basically, If a somewhat similar device is already on the market, the FDA will clear the new device for the market.
[0] https://www.fda.gov/medical-devices/device-approvals-denials...