Looks like Microsoft is keen on bringing Cortana up to par with Google’s and Apple’s own digital personal assistants with the new features they are throwing in. Marcus Ash, the group program manager for Cortana on Windows Phone, tweeted that their team is currently working on passive voice activation for their service. This would mean you no longer have to hold the search button or tap on the live tile to activate Cortana. You would just need a voice command like when you say “Ok, Google” for Google Now or "Hey Siri," for iOS 8.
Something to think about as we design voice activation for #Cortana. Don't want Jesse sending texts on your behalf. http://t.co/Vq4uXB0P6q
— Marcus Ash (@marcusash) June 17, 2014
Source: Ubergizmo