Ok so it's not true system wide access, but pretty darn close. Using a few apps, and a little jailbreak action, Justin Riley shows us how to control some basic functionality with just voice. Here we demonstrate adjusting the iPod, finding a place to eat, and even posting a tweet.
Open your mind and imagine when iOS 4 comes out and vlingo can be backgrounded. The goal of vlingo is to allow any developer and their application to use the vlingo voice recognition engine to do whatever the developer wants with voice. So eventually everything you ever wanted to do will be able to do with voice.
(p.s) still don't text and drive, even if you can do it with your voice!