I needed to use mobile-fu as a gem in my rails 2.3.8 project. These are the changes I made for that to work.
working on correct gemspec
fixed #9 #11 removed mobile user agent and fixed readme
This project is abandoned. Please see the active fork at http://github.com/benlangfeld/mobile-fu. Please test with the released gem and master branch of the new home for the project, and file an issue on the other repo if you still have problems.