Windows Phone 8.1 (from Microsoft)

PR: Today at Build 2014, Microsoft's developer conference, the company announced several advances to Windows including Windows Phone 8.1.
As part of the Windows Phone 8.1 unveil, Microsoft announced a number of new features.
Windows Phone:
• Cortana - The world's first truly personal digital assistant with a persona inspired by a much-loved HALO character. Powered by Bing, Cortana gets better over time by asking questions based on behavior and will check in before she assumes you're interested in something.
• Action Center - Complements Live Tiles by showing new activities and notifications at a glance.
• Senses - A suite of features that takes the work out of managing data use, storage space and battery life.

Windows Phone 8.1 will start rolling out to current Windows Phone 8 users over the coming months. It will also come pre-installed on new phones starting this month. Cortana will launch shortly in the U.S. as a beta, in the U.K. and China in the second half of 2014, and in other countries in 2015.
(Video from Microsoft PR firm)