First of all most of the inventions are centered around a problem. Well one of the major problems surrounding cellphones today is the annoyance they cause when someone is talking in public both for the talker (who can't hear) and the public who doesnt want to hear what the talker is saying.

1. First cancellation setup(blocking talker to the public) - With a microphone listening what the talker is saying and pumping out the reverse polarity to the public. This would block, or at least muffle what the public is hearing from the loud person on the cell.

2. Second cancellation setup(making it ezier for talker to hear) - With a microphone listening to the ambient sounds of the public, once again polarity is flipped. Two speakers would pump out the opposite waves to both one speaker in the ear, and another to the other ear through a headset attached from the phone over the head to other ear.

Theoretically it is possible but i would think that the speakers would have to be strong enough. The sounds would not be perfectly cancelled but at least it would be muffled at least helping the problem.