I think like double tap to wake.... If it isn't on the low voltage core, like moto x always listening is, its never gonna be battery friendly. But people wanted....they got it...kinda. Better than having to be on a certain screen anyway. Just now audio in is listening to every sound it hears.
Sent from my new HTC One M8, N7, Moto X, GTab3 or S2.

Need help with poor battery life on the N5...or any device really? Lots of info in first 4 posts! >>>>
[Battery Life Help] Troubleshoot Battery Issues Here....and Tips