The FDA has given approval for Envoy Medical‘s Esteem hearing system, the first totally implantable prosthetic for moderate to severe sensorineural hearing loss. 
The system detects vibrations at the eardrum, processes the signal digitally, then applies physical vibrations directly to the cochlea.
Clinical studies showed that 56% had improved hearing with the Envoy Esteem compared to their pre-implant hearing aids. However, 7% experienced facial paralysis and 42% experienced taste disturbance as a result of the surgical implantation of the device. Envoy will follow up with a new study of 120 subjects to further evaluate post-implantation complications and device effectiveness.
Video of how the Esteem works…
Press release: FDA APPROVES FIRST OF ITS KIND, FULLY IMPLANTABLE (SURGICALLY), INVISIBLE, PROSTHETIC HEARING RESTORATION DEVICE…
Product page: Envoy Esteem…
Flashbacks: Esteem Totally Implantable Hearing Device Under Consideration for Approval in US; Esteem Totally Implantable Hearing Device On Track for US Approval
Envoy Esteem: First Totally Implantable Hearing System Gains FDA Approval
March 19th, 2010 
Medgadget Editors ENT