While that sounds like a good idea at first, I think it makes sense to have the microphones at least near the ears.
The frequency content of a sound is directional, and moreso as the frequency increases. As a test, listen for a difference in the highs with your (computer/stereo/home theater/whatever) speakers both aligned with your ears, and not. Due to this directionality, a microphone in your shirt pocket would pick up a sound differently than one near your ear.
The brain does some very fancy and clever tricks based on the differences in the timing and phase of a sound as it arrives in both ears to determine things like relative position and distance. Having the hearing aid mics receiving sound similarly to your ears would should make it easier for the brain to continue to do these nifty tricks.
Otherwise, yeah, put the amp and other circuitry in your shirt pocket or wherever else is convenient. It should be a lot easier and cheaper to fit an amplifier and multi-band compressor in your shirt pocket, than in a tiny sliver of plastic that has to fit behind the earlobe.
The frequency content of a sound is directional, and moreso as the frequency increases. As a test, listen for a difference in the highs with your (computer/stereo/home theater/whatever) speakers both aligned with your ears, and not. Due to this directionality, a microphone in your shirt pocket would pick up a sound differently than one near your ear.
The brain does some very fancy and clever tricks based on the differences in the timing and phase of a sound as it arrives in both ears to determine things like relative position and distance. Having the hearing aid mics receiving sound similarly to your ears would should make it easier for the brain to continue to do these nifty tricks.
Otherwise, yeah, put the amp and other circuitry in your shirt pocket or wherever else is convenient. It should be a lot easier and cheaper to fit an amplifier and multi-band compressor in your shirt pocket, than in a tiny sliver of plastic that has to fit behind the earlobe.