Android phone users and specially Jellybean users you can start now checking for the new update release for your device. the first devices to get the KitKat update are not Google's NEXUS this time as usually, but Google's owned Motorola jumped to the head pushing out KitKat 4.4 in the United States just three weeks after announcement. 
The new android KitKat with more polished design, improved performance and new features as for users as for developers. from the main features we can notice the android 'voice search' improved as it comes to the head the iPhone's Siri, Kitkat's "OK Google" will answer your questions and can even play a song for you. just say "OK Google" and your phone will hear you and voice search will be lunched. also a smarter caller ID is one of the whole changed design in KitKat and we can't forget the Step detector ; Android 4.4 also adds platform support for two new composite sensors ( step detector and step counter) which track steps when the user is walking, running, or climbing stairs. we can also notice some improvements to the phone dialler, Gallery photo editing, and support for Square's credit card reader and support for secure NFC-based transactions through Host Card Emulation (HCE).
However many smartphone manufacturers will get more time to lunch the new android KitKat, as many devices need to update for the jellyBean first, like the new Sony devices which will get JellyBean updates at first and Kitkat later...
