A member of the Android Central forums by the name of dmmarck has managed to get the Camera and Gallery apps from Android 4.2 working on Galaxy Nexus devices running Android 4.1.1.
Unfortunately the new Photo Sphere function isn’t quite ready yet, but we’ll be sure to provide updates as they happen.
Head on over to the forum thread to grab the APK, and be sure to read the installation instructions.
Update: Photo Sphere works!
Android Police have released a flashable zip that enables Photo Sphere taking and viewing, as well as all of the new gallery features.
Update 3: Aaaand they’re gone.