This is a big step forward. For the first time, iPhone 3GS users can live-stream from their devices over 3G networks (and also  over Wi-Fi, of course).

I personally tried it today, broacasting live from the Spanish Language Royal Academy, in Madrid, Spain, and it worked fine.

For that, you need to download the Ustream free app from Apple's Store.

In addition to live-streaming, the app has cool features that allow users to upload their videos to YouTube, MobileMe and Facebook. Ustream also makes it easy to send notices on Twitter when a user has started a live stream.

The release of the Ustream Broadcaster app comes just about a week after the Knocking Live Video app was approved by Apple, enabling viewers to share live video feeds on a one-to-one basis.

Now that the door is opened, expect more apps to include similar live broadcasting capabilities.