I was just thinking yesterday about Augmented (smart) hearing.
Have a BT device in your ears that picks up low frequencies (too low for humans) and bumps it up to audible, same with ultra high frequencies as well.
Also would come with ANC and a smart phone app to tune the device to reduce certain sounds (eg. CT train rumble noise). Could also be used to tune into to human frequencies in certain environments and say .... tune OUT kid noises in others.