If you have a Made for iPhone hearing aid, you can use iPod touch to adjust its settings to suit your listening needs.
Adjust hearing aid settings and view status. Go to Settings > General > Accessibility > Hearing Aids, or set the Accessibility Shortcut to open Hearing Aid Control. See Accessibility Shortcut.
For shortcut access from the Lock screen, turn on Settings > Accessibility > Hearing Aids > Control on Lock Screen. Use the settings to:
Check hearing aid battery status.
Adjust ambient microphone volume and equalization.
Choose which hearing aids (left, right, or both) should receive streaming audio.
Control Live Listen.
Use iPod touch as a remote microphone. You can use Live Listen to stream sound from the microphone in iPod touch to your hearing aids. This can help you hear better in some situations by positioning the iPod touch nearer the sound source. Triple-click the Home button, choose Hearing Aids, then tap Start Live Listen.
Stream audio to your hearing aids. Stream audio from Siri, Music, Videos, and more, by choosing your hearing aids from the AirPlay menu 
.