Microsoft is starting to distribute Windows Phone 8.1 to existing Lumia devices this week. The Lumia Cyan update provides the full Windows Phone 8.1 software, alongside some tweaks and customizations specifically for Lumia handsets. Windows Phone 8.1 includes a personal digital assistant in the form of Cortana, a number of new customization features for Live Tile layouts, a new Word Flow keyboard, a notification center, and much more. The Lumia Cyan part of the update includes a motion data app that collects data for fitness apps like Bing Health & Fitness or Active Fitness. It also includes Bluetooth 4.0 low-energy support, mircast options, and improvements to the camera algorithms for the Lumia Icon, Lumia 1520, and Lumia 930 for improved low-light performance, better color reproduction, and auto-focus improvements.