Now it's official. There exists an open-source project that has released a native iPhone client library for Lightstreamer.
The project, created by Gianluca Bertani, is named iStreamLight and is hosted on Google Code. It is fully compatible with Cocoa Touch and the iPhone SDK 2.1 and requires Lightstreamer Presto or Vivace on the server side.
Below is a video showing a demo application which employes the iStreamLight library, running side-by-side with the home page of the Lightstreamer site.