Older devices such as the Google Nexus S were popular phones that Google and Samsung worked on together. Source code for ICS was released officially into the AOSP in late 2011, and Google Nexus S users got a taste of Android 4.0 Ice Cream Sandwich on their devices quite shortly after that.

The upgrade proved to be a smashing success, offering new UI elements and an awesome set of features. However, there is one thing that the upgrade missed out–Face Unlock, arguably one of the interesting highlights of Ice Cream Sandwich.

The reason behind the missing feature was the Google Nexus S's front-facing VGA camera. High-end phones such as the Galaxy Nexus sport a secondary camera of at least 1.3 MP that is also capable of 720p video recording.

While some people consider the Face Unlock feature an overhyped marketing scheme to lure consumers into purchasing the Galaxy Nexus, others find it one of the coolest, innovative features found in Ice Cream Sandwich.

If you think that Ice Cream Sandwich isn't complete without Face Unlock, then you're just one of the many users out there dying to try out this new feature. However, in the case of the Nexus S, it requires flashing your phone, which unfortunately voids your warranty and may affect your phone's normal functionality. If you are still eager to install it on your device, do so at your own risk and do not hold us liable for any damage to your phone arising from your use of this guide.

Requirements

You need the following to be able to use the instructions in this guide:

• A rooted Nexus S (GSM variant) with bootloader unlocked and with custom recovery installed on the device.
• The device must be running an ICS build. You can check your phone's current firmware by heading to “Settings > About Phone > Firmware Version”.

Instructions

Follow these steps to install Face Unlock on your Nexus S:

1. Download the latest Face Unlock package from here and save it to your computer.
2. Connect your phone to your computer using a USB cable.
3. Copy the downloaded ZIP file to your phone's SD card. Be sure not to place the file deep in the subfolders.
4. Reboot your phone into recovery mode. You can do this by pressing and holding down the Volume Up key and then pressing the Power button.
5. Once inside recovery mode, select the option “install zip from sdcard”.
6. Select “choose zip from sd card”.
7. Select the downloaded file which you have saved in your SD card.
8. Wait for a few moments for the installation to finish.
9. Reboot your phone after the installation process.

Congratulations! You have successfully installed Face Unlock feature on your Google Nexus S (GSM).