MIT Technology Review checked out the of fully implantable hearing aids, one of which is developed by the folks at Envoy Medical, while the other comes from Otologics of Boulder, CO. Called 'Carnia' the hearing aid is accompanied by four separate pieces that are devised to be countersunk into the skull, including a microphone the size of a fingernail that sits behind the ear and a main processing unit that also houses the rechargeable lithium-ion battery that powers the device. The battery gets reloaded by a charging unit that's held in place with a magnet and must be worn for an hour or two a day.

Early users have given full marks to this device admitting that Carnia delivers a "natural feeling of hearing." However, the device still has a long ways to go, with the study currently only having twelve of the 70 to 80 users it needs to complete "phase II" of the trials. Consumers will have to chip in a cool $20,000 to get their hands on 'Carnia'.

Source