Of course current implants are really bad compared to natural hearing, and only implanted to people whose alternatives are even worse. The technology I'm talking about doesn't exist yet.
I arrived at this view because humans are a visual species. Even if you can build a digital camera that's as good as the eye or better (currently you can't, at least not at the size of the eye), the task of processing the data so that it can be used for nerve stimulation would be beyond any computers at reasonable sizes. On the other hand, we can build really good microphones that are more sensitive than human ears and can do a ton of processing that makes such a device worthwhile.
The optic nerve has 770k-1.5M axons while the cochlear nerve has only 30k. Over a magnitude of a difference.
So I believe that a augmented reality kind of experience with devices built under your skin will be limited to ears first, simply because it's easier to pull off technically. Everything else would still have to travel through your pupils in some fashion. 2OEH8eoCRo0 was talking about technology under your skin. Google glass, vr glasses, or even lcd screen contact lenses wouldn't fall under that definition.