You can send a control signal through your AirPods by double-tapping them. These signals can pause your audio, advance to the next track, or activate Siri. You can customizing what tapping each AirPod does in your Bluetooth settings on your iPhone.
A new feature in iOS 12 allows you to use your iPhone's Live Listen feature with Apple's AirPods, a much cheaper alternative than actual medical device hearing aids. The audio comes from the iPhone's microphone, so you can place your iPhone in a better position to hear someone and leave it there. You can even use it as a way to listen in to what is going on in another room.