This just in from IFA: Microsoft announced a brand new Lumia update called Denim, that will let you activate Cortana with a jaunty "Hey Cortana!" just like "OK Google" on Android. Yep, Cortana will now be always listening for your voice.
There are also a bunch of camera improvements to launch the camera app faster and support for 4K recording. Availability: Q4. [Pocket Lint]