This type of "Digital Therapeutics" might be paid for by German health insurance companies. For example, https://gaia-group.com/en/ appears to be a successful provider of medical apps.

If you don't mind, please email me at moin@deutscheki.de and explain in a bit more detail what the needs of that deaf community are. Maybe I can forward that to the right people to get my government to pay for the app that you wish to see developed.

I mean I agree with you, it certainly would increase life satisfaction for deaf people if they could "listen in" into conversations to know what others are gossiping about.