If headphones are too bulky and ear buds make your ear canals hurt, why not surgically transform your ear itself into a speaker? That’s what body hacker Rich Lee has done, by implanting rare-earth magnets in his ears, so he can listen to music or amplified sounds even when he’s not wearing headphones.
In addition to music, he looks forward to connecting these embedded bio-speakers to a directional microphone or a voice analysis app, so he can do surreptitious spy-like activities, like listening to conversations across the room and detecting whether you’re telling lies or not. He’d also like to connect his setup to a Geiger counter, so he can get ambient readings on radioactivity, or perhaps use it as part of a digital echolocation system of some kind.
He first implanted magnets into each ear’s tragus (the flap of skin and cartilage that sticks out in front of your ear). No licensed surgeon would be willing to do this procedure, so like many transhumanists, he had to get a friend to do the operation for him.
To make these magnets into a speaker, he wears an induction coil around his neck, connected to an amplifier and, through that, to his phone. The varying currents in the coil cause the magnets to vibrate, exactly as they do in a speaker — except in this case, the magnets are part of his actual flesh.
That was building on the Instructibles project Make Your Own Invisible Earphones