Well, it was only a matter of time before Google pushed its "always-on" technology to all Android smartphones. I actually warned you about this when it first debuted on the Motorola Moto X.
The "OK Google" technology allows you to make use of your sleeping gadget when it is out of reach or your hands are full. You simply say "OK Google" and the phone will light up.
We heard some rumors that Google would be trying to bring the yell-at-your-phone-from-anywhere superpowers the Moto X has to all phones, and while you'll have to have your phone plugged in to get it to work with the screen off, it's a step in that direction. And one that won't completely devour your battery. Hopefully.
"OK Google" is available with the Android 3.5.14 update. There isn't a specific date for when it will be available for each phone, so just look for the update if this is something you are interested in.
The Google Search app update will also include a Voice History section that stores your old commands, so it can better recognize your voice. Thankfully, Google also allows you to delete your recorded audio history.