With the plethora of cell phone cameras, sending a live video stream could be extremely helpful to first responders. Further, if it's a shooting situation, kidnapping, or bank robbery, the cell phone user may not be able to speak for fear of harm, but could be able to to silently text or send video.
According to Wired, "In a press release announcing Tuesday’s changes, the FCC pointed to the now-infamous shooting rampage at Virginia Tech as an example of how a more modern system could be useful."
Now the question is who will make the first prank call to 911 sending lurid or sexual pictures or video to the 911 dispatcher?