I spent a few years at Intel's Digital Health Group (we had a phalanx of PhD's and MD's on staff trying to answer your question). As others have mentioned, this is a very crowded and complicated space. Even more so if the device needs FDA approval. Since you lack deep domain knowledge, step 1 is finding a partner (ideally a clinician with many years experience) who has it, and also has a nose for business opportunity. Let them guide you toward a problem that needs solving.