Firstly, this zip is only available for Galaxy Nexus phones that are rooted. All others need not apply. Sorry. If you’re packing a rooted G-Nex with a custom recovery installed, follow the instructions below. Also, some people are reporting bugs with Photo Sphere – mine worked fine, but just know that there are issues for some.
Instructions:1. Download the 4.2Camera.zip (mirror) file.
2. Place the zip file on the root of your phone’s storage.
3. Reboot into your recovery.
4. Just in case, make a backup.
5. Flash the 4.2Camera.zip file. (No need to wipe anything)
6. Once installed, reboot your phone.
7. Lastly, enjoy it!
from Droid Life: A Motorola Droid Blog