http://www.agilewebdevelopment.com/plugins/label_helpers
Not a form builder, but you can presumably use the same technique.
HTH, Michael
I have no idea, but a local copy 
See below for label_helper.rb
HTH, Michael
http://www.eric-stewart.com/blog/articles/2006/01/13/label-me-please
# Helpers for generating label tags for inputs