As Microsoft rolls out the Lumia Denim update, one feature those with newer Lumias are looking forward to is 'Hey Cortana'. Based on passive-voice activated technology similar to the Kinect, the forthcoming feature lets users call up Cortana by merely using their voice. The feature works even when the Lumia is in standby with the display off.
The images and accompanying video, shown below, come from the site MSFTPlace who picked up the Lumia Denim update on their Lumia 1520. As they note in their article, Hey Cortana is not yet available in Spanish, so they needed to change to English in order to enable the feature.
In the posted screenshots, the tutorial for Hey Cortana informs the user of how to set up the feature. The individual is instructed to be in a quiet room to train the app to recognize their voice. Once done so, Cortana can be called upon when the device is in standby.
Google already has a similar feature on the Moto X series, but this is Microsoft's first attempt at bringing it to their Lumia line (it is not clear if the HTC One will get it as well). Currently, only the Lumia 930 (Lumia Icon) and Lumia 1520 are known to be able to use 'Hey Cortana' due to their use of the 800-series Snapdragon.
Source: MSFTPlace; Thanks, Gabriel, for the tip!