Google Now available for download and installation on ICS AOSP ROMs. It is apparently not working on phones in Asia but users from the US are welcome to
- Open Root Explorer & navigate to /system
- Now Open build.prop in Text Editor.
- Edit ro.build.version.sdk = 16 & save.
- Now go to /system/app & Rename GoogleQuickSearchBox.apk toGoogleQuickSearchBox.apk1
- Now reboot & install the app from the download link.
- Now edit build.prop & change ro.build.version.sdk = 15 & reboot.