The new Galaxy S4 and HTC One Google editions ship with a new improved camera app. The new camera app is built with features like PhotoSphere and an improved settings menu. The new app is a part of Android 4.3.
You can install the new camera app any Android phone running Android Jelly Bean (4.2), it works on phones running 4.1 and Ice Cream Sandwich (4.0). You can simply install the APK file just like any other app and get to use the new stock camera. No rooting required for this process.