I recently got the Nexus 5, and was disappointed at the lack of the “always listening” feature of the Moto X. I’ve tried alternatives like Open Mic+, but they all leave something to be desired.
I decided to see if I could modify the Motorola Touchless Control app that runs on the Moto X to run on the Nexus 5, which has a Snapdragon 800 processor. The Snapdragon 800 has a dedicated core that should be capable of low power audio processing.
What I found was that Motorola is using Nuance’s Dragon Speech Recognition Software to perform some of their speech recognition. This is the same software that powers Apple’s Siri, and Samsung’s S Voice. This is interesting, because Motorola is owned by Google, which has its own set of speech recognition services. Including this feature from the Moto X in Android 4.4 would likely have meant that Google would have to pay royalties to Nuance for every handset sold running 4.4
This probably explains why the “always listening” feature didn’t make it into Android 4.4 KitKat.
Here’s a screenshot showing the com>nuance>dragon>toolkit folder within the decompiled Touchless Control APK.