With their wallet, about as far as they want.
Nonsense, you obviously don´t know how the FDA and other regulatory organisations work. Big pharma with bulging pockets are struggling with the FDA every step of the way. They would be the first to buy them out of their processes, but they can´t. Money is not a factor in this.
There are very strict regulations for medical devices that are applicable to all, also Apple. Deviating from those for money would set a dangerous precedent and would make additional rules necessary in an environment that already is complicated enough as it is.
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that's a great question, i would assume as long as they don't claim that their product can heal or cure you of a disease they wouldn't really ever need approval.
No, it goes beyond that. Apple or any manufacturer needs approval for devices that are classed as medical devices. Examples are point of care devices such as blood pressure monitors or blood glucose monitors. These do not claim to heal or cure but assist in the management of diseases such as hypertension and diabetes.