[citation][nom]Parsian[/nom]that is true, but the intensity varies. I wonder if it influences your nerves to act funny after a while. I mean, right now, not many people use such devices, but who knows what it could do to you health wise. But then again, using your keyboard and mouse for long duration will have health issues as well.[/citation]
Actually, lots of people use devices like this. In cases of extreme hearing loss, doctors will sometimes embed a stainless bolt directly into the skull behind the ear. A hearing aid is then fitted to the ear, and passes it's output into the bolt via vibratory conduction.
And as was mentioned above, the Navy has been using bonephones for quite some time.