There are lots of apps available for iOS and android users which assist people with hearing impairment to communicate, socialise, and enjoy entertainment more
The basic concept of apps is the same, it receives the audio input from phones microphone, amplifies it (by applying algorithms) and plays it in the headphones, thereby creating elementary hearing device. The additional and more advanced features bring the app closer to a real hearing device.
There are also apps available for testing different aspects of hearing loss and prevention.
You can find more information about hearing apps at following websites: