Qik is a live video streaming service with mobile applications for BlackBerry, Nokia and Windows Mobile devices. There was a version for Qik (iTunes link) a year or so ago for jailbroken iPhones, but they have not been able to get a version up on the App Store until now. As you can read in their announcement blog post you are not yet able to live stream, but you can record a video (with your iPhone 3GS) and then have it uploaded automatically if you are connected to a WiFi network. A version for 3G uploads has been submitted for approval so an update should be coming soon.
While this isn't currently live streaming like their other clients when they get the 3G and WiFi support both then it will be pretty close and probably a bit more reliable than live anyways. You can start now by uploading existing videos you captured and I personally like how easy it is to look through your camera roll and then upload videos. I actually paid for a video uploading application to get my videos on Facebook (didn't work all that great) and now Qik gives me the ability to upload them to Facebook, Qik, YouTube, and the other networks Qik integrates with. I need to test it more, but have hopes their service will be more reliable.
You can also shoot your video in horizontal or vertical orientation to best capture the moment. Location sharing is also supported with Qik for the iPhone 3GS. Since no other iPhone models capture video this version is limited to the iPhone 3GS.