Today, Google has started rolling out Android 5.1 update to all Lollipop compatible devices. This update comes with number of bug fixes and few new features.
Android 5.1 comes with multiple SIM support. So, users with dual SIM devices will get benefit. It also has Device Protection which helps in managing and tracking your lost phone. Your lost phone will be locked until you enter your Gmail account credentials even if some resets your phone via hard reset.
It also supports for HD voice. So, you will get crystal clear sound while talking to your friends via compatible devices like Nexus 6. There are few other tweaks like you can quickly manage your wi-fi networks and paired Bluetooth devices directly via quick settings bar.
Nexus 6 users will instantly get the update. Other users will get this update in coming days. You need to keep checking the software update section of your devices.
Source: Android Blog
