(Updated with BBC commentary) The early indications of a beta iPlayer client for the iPhone have been confirmed. Beginning today, mobile visitors to the iPlayer website can now watch a limited number of BBC TV shows, such as Whistleblower. The video has been specially converted to cope with the limitations of Apple's Safari browser, which cannot play Flash; it is most likely then that episodes are being encoded in streaming QuickTime.
All versions of iPlayer let users watch the last seven days of BBC programming for free, as a service to those paying the TV license fee. As such it is only available within the UK, and the only client that supports downloading videos at present -- as opposed to streaming -- is the Windows version. A Mac client is in the works for sometime this year though, and it may be joined by an Apple TV version.
Update: The BBC remarks that iPhone streams use 400Kbps H.264 video, with a 116Kbps AAC soundtrack. Because of this, the iPhone can only access content through Wi-Fi, as EDGE access will always be too slow.