[alistairSH]

In the US, it's a bit of a mix.

There are ~3 categories of hearing devices in the US... 1. Prescription hearing aids - go to audiologist, pay $$$$$$ for devices 2. OTC hearing aids - AirPod Pro etc - less money 3. PSAP - Personal Sound Amplification Product

In theory, from top to bottom, you loose features and complexity. But, I haven't been able to find a good summary of technical requirements for each tier of device, just vague language.

Very generally, PSAP is a "dumb" amplifier - all frequencies get amplified - often used by hunters and bird watchers to hear animals.

What I can't figure out is the difference in requirements between OTC and prescpription - is there some feature that Apple CANNOT deliver OTC that a prescription device may?

[observationist]

The only real constraint now is volume - there's still a hard db limit of 111 db because of the technicalities of medical device categorization. Software and hardware patents are entwined with the medical device nonsense and the hearing cartel is incredibly litigious. They make FAANG look like playground bullies if they feel their territory is being infringed on, and have an absurd breadth and depth of patents covering every possible iteration and permutation of audio technology they can possibly get away with.