Hi rozannethomas
welcome to this Apple (user-to-user) Community.
Re " ... for someone with Parkinson's disease who uses a voice amplifier is there and amplifier that will use Airplay so it can be heard on an iPhone?"
Sorry there have been no replies to your post so far.
Apple support's articles may or may not help:
Eg: This article has a "Get suggestions" link at the bottom: Use AirPlay to stream audio - Apple Support
and
If screen mirroring or streaming isn't working on your AirPlay-compatible device - Apple Support
has a link to "Home" accessories
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If you still need help: You may want to try reaching out to the experts at Apple:
How to contact Apple for help with accessibility features - Apple Support