Google Now Launcher has been updated to work with all devices with android 4.1 upwards. Google has slowly sectioned off every part of its operating system in to an app to make it easier and faster to perform updates without the need for carriers to get involved. Details of the app are –

Upgrade the launcher on your device to make Google Now one swipe away. From your primary home screen, swipe right to access Google Now cards that give you just the right information, at just the right time.
Available on all devices with Android 4.1 (Jelly Bean) or later.
Key features:
• Google Now on your home screen – it’s easier than ever to get just the right information at just the right time.
• Just say “Ok Google” – when you’re on your home screen, just say “Ok Google” to trigger voice input. Then say your search query. Or tell your phone what to do, like send a text message, get directions, or play a song.
• Faster search – tap the search box and you can enter your query immediately.
• Easy access to your favorite Google products and services, like Gmail, YouTube, and Maps.
• Larger viewing area – the status and navigation bars are now translucent, so your wallpaper pops from every pixel, and is even visible when you expand your apps drawer (when supported by device).
• Intuitive wallpaper picker – select any image that’s stored on your device, or in the cloud. Position and preview your wallpaper before you set it.

Head over to the Play Store for more details – https://play.google.com/store/apps/details?id=com.google.android.launcher&hl=en