With the help of tcpflow and the current Hue iPhone-application, I’ve managed to capture parts of the Hue API. As a result of this, I’ve begun working on a complete Hue API reference — available on GitHub at the Ruhue repository.
A few notes about the Hue hub API:
Further details can be found in the Ruhue GitHub repository. It will be updated as the API calls are explored. Pull requests are very welcome, so fork away and send patches and I’ll accept them into the repository!
In addition to the GitHub repository, there is also a Google Groups mailing list, Philips Hue Hackers, a mailing list for anybody exploring their Hue lights. Expect a lot of technical discussions on this mailing list.
The mailing list e-mail address is firstname.lastname@example.org.
The Ruhue repository contains a console script, allowing you to use an interactive ruby interpreter to control your Hue lights. Further details are in the Ruhue README.
A few others have begun exploring how their Hue lights really work as well, and have written articles about their own progress. These articles existed before I started the documentation effort, and they’ve helped immensely.