All-in-One Head Mic and Speaker Vest

I am aware that one can use a spiralled conductive thread pattern on a piece of material and with a magnet in the middle extract sound from it. What I would like to do is design a vest of sorts with a large spiralled conductive thread and magnet at the back and two more smaller ones on the front two panels of the vest. With a headmic, lithium batteries and a small amplifier built into the vest, a person will be able to address a group of people like a class or meeting without the hassle of a portable speaker being placed somewhere in the vicinity. The person will have these speakers with him/her on the body all the time which means the sound is coming directly from him/her. It would be even better if the vest and amplifier was solar-powered so that charging and maintenance is kept to a minimum. The question now is, can it be done? Will the vest get too hot or, if it's made of a net-like material, would that help? I know conductive thread is not that expensive and there are also small cheap amplifiers on the market (every audio device has one in nowadays no matter how small). So, is there someone who is able to make a cheap prototype? I know the material is inexpensive to obtain but the secret lies in the brains behind the project.