Google announced that they are rolling out Android 5.1 Lollipop, an update which improves stability and performance along with a couple of new features such as support for multiple SIM cards, Device Protection and high definition (HD) voice on compatible phones. This would be the first major update to Android Lollipop since its release.
Google made the announcement on their Official Android Blog where they mentioned that Android 5.1 Lollipop will also provide enhancements such as the ability to join Wi-Fi networks and control paired Bluetooth devices directly from Quick Settings as well. It also added that with Android Lollipop 5.1, users can now use more than one SIM card on a device with multiple SIM slots.
An additional feature called Device Protection has also been added in situations where if you lose your phone or if its stolen, it will remain locked until you sign in with your Google account, even if someone resets your device to factory settings. According to the blog, this feature will be available on most Android phones and tablets shipped with Android 5.1 in addition to Nexus 6 and Nexus 9.
The Android 5.1 Lollipop update will also bring in high definition voice calling on mobile phones. Dave Burke, VP of Android Platform posted on the blog that users will get crystal clear calling with HD Voice between compatible Android 5.1 devices like the Nexus 6 on carriers such as T-Mobile or Verizon.