One constant never changes in the Android universe: if a device comes with something that can't be removed, someone will find a way to remove it. If a device comes with something you can't get anywhere else, someone will find a way to port it over.
That is just as true for the Galaxy S III, which is why the XDA Developers forum has been full of related topics lately, both with custom ROMs for a device that hasn't been released, and ways of getting S III features onto other devices. S Voice may have gotten the most attention, but there's an ocean of goodies out there.
Galaxy Nexus + root "conversion kit"
If you have a Galaxy Nexus, there's a Galaxy S III add-on available that you flash through CWM Recovery in order to get the complete package in one go. From the water drop sound when you unlock the device to the look of the settings menu, the launcher, and apps like S Voice, this is a all in one solution.
It's rather ironic seeing this on the Nexus, since one of its big selling points is that it comes with stock ICS, not any sort of manufacturer customization. To slap Samsung's TouchWiz on it seems a bit weird, but then again that's what Android is about: choice. With the Nexus size, resolution, and screen type being almost exactly that of the S III, and with a lot of people not caring about the S III's faster chip, better camera, SDXC slot etc, this is after all a way to get a pseudo-S III for much less.
If you don't have a Nexus, or if flashing files via CWG Recovery tells you nothing, a lot of the S II Content has been pulled in a more traditional fashion as well. There are tons of these threads on XDA, but the ones that stood out are the one that has the applications and the one that has the media files.
I tried a few of these myself, specifically I played with the water ripples/dandelion live wallpaper and had a listen to the ringtones and the notification sounds. I pulled the new version of the Over the Horizon melody and put it on my S II, complementing the S II's version. I quite like that tone and use the S II version as my ringtone (first of the two in the video above), while the much softer, slower S III version now serves as a soft alarm sound.[XDA via Droid-life]