This is the real deal, called also Dynamic Streaming; as envisioned by Apple!
Feed currently offline... The example is not always working, because we might leave the test url without data, but you should be able to see/hear at least the last segments... If the browser thinks you have enough bandwidth you'll see video, else just audio.
In this example we have four available streams encoded. We use 48k audio, 240k video and 440k video streams.
The device browser will choose the correct line speed and play the stream most adecuate on the fly.
The video source is our office kitchen clock, the audio source our programmer's iPod. Camera and capture on an iMac, segmenting on a 17" powerbook.