This would be awesome, but I believe the Moto x and other Android phones that have this usually have one cpu core dedicated to listening for "okay Google"
Correct. Moto X has a special chip that uses almost zero battery to listen for voice commands. They introduced the feature two years ago. I think Apple product development takes 3 years so maybe it's still in the works for iPhone 6s. A lot of us thought Apple would do this for the iPhone 6 but then we also thought we'd get 2 gigs ram lol. Anyway I'm still happy with the new Siri functionality. Siri has really, for the first time, become useful in iOS8. Siri has come into her own.