Using the proximity sensor on your phone, it detects when you wave your hands over the screen or when you place the phone to your ear.
When your hands or ear close to the proximity senor, it will auto answer the received call.
If you driving the car, you can auto answer the call.
Air call Accept/Receive is based on proximity sensor. You just wave your hand over a proximity sensor for accepting or rejecting call. and also play,pause,next,previous music track.
You simply using this application as air call answer/Air call accept.