Those exist. Main application is military/police radio, because you can use them even with a gas mask on. Disadvantages are that you need to fully speak (whisp

Those exist. Main application is military/police radio, because you can use them even with a gas mask on. Disadvantages are that you need to fully speak (whispering and sub-vocalizing doesn't work), and your voice sounds kind of funny. Keywords is "bone conduction microphone" or "ear bone microphone".