Check out these links:
Everything You Didn't Know You Could Do with Google's Voice Commands
Inside Search ? Google
On Jelly Bean, Google Now and Google Search are one and the same app. When you said you disabled Google Now, presumably that meant you disabled the cards. If you tap the microphone you should still be able to use the new voice commands.
Previously, you had to use very precise syntax to make commands but now you can speak naturally to it and it?ll get it more often than not.
I?m aware that there are folks like you who don?t trust Google Apps due to privacy concerns. I don?t get it, but I?m not one to judge.
Anyway, if you are indeed concerned about the privacy issue, you probably shouldn?t use the voice commands. What happens is your commands are sent to Google?s servers to interpret the meaning. You probably don?t want that happening.