Wild speculations on the Moto X based on the Rogers video...
I've seen the leaked Roger's video several times, and here are some wild speculations based on it:
1) There's a small dot (looks reddish) at the bottom bezel. At first I thought it was an LED indicator, but its wirdly positioned a little off center, and it isn't exactly glowing. Plus, they clearly say the new on screen notifications replace an LED.
So what is this? My guess is that this is a motion sensor. Nothing so dramatic as a Kinect or Leap Motion, but I think it lets the phone know when you're looking at it so it can show you notifications. Similarly, it can distinguish between a car driver and a passenger, so it knows to amp up the voice command and car-friendly interface if the owner of the phone is driving.
2) The video says the phone will learn your voice. This strongly implies voice recognition to me. And I think that is critical to avoid the always on features from being misused by people who don't own the phone, or accidentally speak near it.
3) I'm guessing we'll see a special Motorola headset, or a way for normal headsets to integrate, so that the always on features work via the headset mic as well. This is critical, since this ensures that Google Now can be used completely handsfree.