If Harry Potter had a hearing aid, instead of program settings there'd be spell settings:
Reparo to fix any malfunction.
Nomore Uhdawax to clean it.
Vox Heliuma to make Draco's voice sound like he'd been inhaling helium.
Amplifario to make Hermione's helpful whispers in class louder.
Maybe with a deluxe model, he could even use Translatia Comprehenso to understand foreign languages.
Or perhaps his hearing aid would be just a hearing aid, the way his glasses are simply glasses.