It was good while it lasted! The S Voice application from the upcoming Samsung Galaxy S III was extracted from the shipping ROM that was leaked and was made available to other Android devices. According to reports, it was working pretty well on ICS-powered phone, like the Samsung Galaxy Nexus, that is until Samsung blocked the servers.
According to recent reports, users on non-Galaxy S III devices are getting errors when trying to operate the leaked S Voice app. According to the community, the application sends out a lot of information to the servers, including your device’s make and model, so it’s pretty easy to filter out usage server-side (which is a Vlingo server in the U.S., in case you’re wondering). Until there’s a workaround you will not be able to use one of the Galaxy S III’s main selling points.
Update: And it looks like the community is already working on a tweak. It appears that you can try and edit your build.prop as described in the source link below to trick the system into thinking you have a Galaxy S III device.