Android 5.1 Lollipop changelog:
Support for multiple SIM cards:
Whether you want to share your phone with a family member or better manage your mobile costs, Android Lollipop 5.1 now lets you use more than one SIM card on a device with multiple SIM slots.
With Device Protection, your lost or stolen device will remain locked until you sign in with your Google account – even if someone resets your device to factory settings. This feature will be available on most Android phones and tablets shipped with Android 5.1 in addition to Nexus 6 and Nexus 9.
High definition (HD) voice on compatible phones:
High Definition voice calling is now on your mobile phone. Get crystal clear calling with HD Voice between compatible Android 5.1 devices like the Nexus 6 on T-Mobile or Verizon.
Quick settings enhancements:
Android 5.1 Lollipop also provides enhancements such as the ability to join Wi-Fi networks and control of your paired Bluetooth devices directly from Quick Settings.
Stability and performance improvements.
Nokia has been known for supporting its devices with latest software updates and the latest OTA update for Nokia N1 brought Android 5.0.2 that only a handful of lucky Android device owners had received yet. So, we can look forward to Android 5.1 making its way soon to Nokia N1.