I just deployed API token support to Lighthouse tickets. You should be able to use any valid token for index/show actions, and a writable one for create/update/destroy. This is just a preliminary message if anyone wants to start hacking before I get the basic docs written up.

http://ar-code.svn.engineyard.com/lighthouse-api/

Checkout the trunk versions of activeresource and activesupport to the vendor directory until an official ActiveResource release is out.

Does the message resource work as well? Or does it require user authentication?

Not yet, but you can track my progress at the API Docs. It still needs some css and liquid cleanup. (We have a post on the blog coming with the new Lighthouse changes deployed on Monday)