Here's a new (unreleased) hearing aid that you wear over a back molar. It uses a wireless mic behind your ear to transmit sound to the tooth-unit, which then retransmits the sound through bone conduction — without having to drill pins into your skull or surgically embed hardware, which is then hard to upgrade when the field advances.
SoundBite detects noise using a microphone placed in the ear connected to a transmitter in a behind-the-ear (BTE) device. The BTE transmits to an in-the-mouth (ITM) device that sends small sound waves through the jaw to the cochlea. There is no surgery needed, and both the BTE and ITM are easily removed to be charged inductively. Sonitus Medical is still preparing the SoundBite for eventual FDA trials for single sided, and (eventually) other forms of deafness.