A company called Sonitus Medical is currently working on a new type of hearing aid for people with single-sided deafness, one that uses vibrations in your teeth to allow you to hear again.
The small device would connect around the teeth and use bone conductivity to take sounds from a microphone in the deaf ear and turn them into vibrations that could be heard by the working ear. Pretty crazy! It's currently being tested, with plans for it to hit the FDA next year for approval and then official release. [New Scientist via io9]