HTTP live stream technology is now required for streaming video according to Apple's new iPhone developer RSS feed.

An innovative feature of iPhone OS 3.0 is support for HTTP Live Streaming technology. One of the great benefits this technology delivers is the ability to dynamically adjust to varying network bandwidth conditions. It lets you store multiple video clips of different quality on the server, and then deliver the one that matches what the requesting customer is capable of viewing given the network they have access to. Use of it is now required for all applications which deliver streaming video. You must include a low quality stream of no more than 64 Kbps for your app to resort to when network conditions demand it, along with the higher quality streams you want to deliver to your customers when the network can support it.

See the HTTP Live Streaming Overview in the iPhone Reference Library for details.

We've read about -- and seen -- HTTP Live Streaming before, but with Apple insisting on it, and companies like Elgato using it in EyeTV to allow streaming to the iPhone over 3G, it could be getting interesting. Concerning EyeTV's implementation, TUAW's Erica Sadun says:

Powered by the EyeTV 3.3 update (free to existing owners of EyeTV software), this technology avoids App Store hassles while providing on-demand video access to your home TV recordings and live programming. [...] As an added bonus, since Mobile Safari has access to the iPhone's TV Out capability (third-party apps can't use it, but Apple apps can), you can use a component or composite video-out cable to display your streamed video on any convenient TV.