I have mentioned in the past that the future of the web will be live video streams on social networking sites. I expect 2-4 video streams at a minimum from people who can't seem to share enough information about themselves. To get an idea of what this will be like I tested a new app called Knocking Live Video on the iPhone with Tom Keating. The idea of this application is to share your camera view with the other iPhone user.
The Knocking application does not transmit voice so the carrier can still rake in voice revenue. So yes, you can talk on the phone and run this program at the same time. One area where this can be useful is in the grocery store where you might want to share what you see with a significant other. Other applications include sharing important moments like a graduation, etc.
While this application does work over 3G it doesn't work that well - it crashed on Tom and I about 7 out of 7 times. Over WiFi we had no problems.
When it worked over 3G we got at least 15 seconds of video each time and the video quality was impressive. I suggest you download this app ASAP because currently it is free and after 50,000 downloads the company expects to start charging.