Rather than a separate chip, could an individual core be dedicated to the task of listening, without killing the battery?
I'm on a Verizon Note 2, and the phone sometimes takes two seconds to wake up after a power button push. This sucks, so mikeyxda put together zero wake lag, which keeps one core awake all the time and eliminates that pesky lag. Because the other cores aren't awakened unless needed, battery life doesn't suffer. http://forum.xda-developers.com/show....php?t=2208267
Could that sort of script be used to keep the phone from burning up battery?