Some related (but not the same) questions:
Listening (eavesdropping) device that can be put into victim's ear? (which is closed because of the need to focus)
Microphone implanted in and powered by the body (most related, yet I want the design to be even further)
I want to design a listening device which is put into the human ear canal of secret agents in some espionage activity, and/or to eavesdrop whatever the victim is hearing. The information (voice) eavesdropped is sent remotely to the receiver or the eavesdropper of a distance. And this device should be small enough to be put into ear canal and stay there. The device is powered by human body (like charged by bio-electricity).
To make this possible we need to power both the microphone and the transmitter, sending signals strong enough to travel a certain distance and be received properly. I wonder, based on the current science and technology, how much power is required for this listening device to work, and to how far away it can send the signal for receiver to get the information. Namely, can the power generated by human body be used to make such device possible, given the conditions above? (Or what are some other handicaps?)