The basic bar I'll use for functional interface is the ability to type with your thoughts.
Commerically available will mean available to the general public, and marketed for sale. Marketed for sale means the device is being brokered for the explicit purpose of making profit: if a billionaire pays someone a lot of money to build them their own personal interface it does not count. It does not need to be affordable. If anyone with enough money can buy one, this resolves as Y.
@AntonBogun In the case where it's prohibitively expensive, but still commercially available for people with impairments, I would resolve this to Y. This is part of a series of chat-gpt generated markets, and I'm trying to keep the resolution criteria closely aligned with the wording of the question. Since it doesn't stipulate "commerically available and affordable" I'll leave that requirement out.
I know there are already some basic computer-brain interfaces making the rounds through research institutions, so I'll update the market criteria to specify what constitutes commercially available.