I think there is a device called delayed auditory feedback device, it essentially replays our voice through earphones or any speaker with a slight delay and frequency modulation so as to aid in speech. I have noticed that when I talk along with others almost like in unison I hardly stutter and this device is based on that. I do not how accessible it is and how many people use it (I have not) but it exists. Maybe something can be done to make it more accessible and also inprove it