Rails 3 ActionView override for Foundation 4 field error styles.

application.rb

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  html = %(<div class="error">#{html_tag})
  html += %(<small>#{instance.error_message.to_a.to_sentence}</small>).html_safe unless html_tag =~ /^<label/
  html += %(</div>)
  html.html_safe
end

Note that this wraps labels and inputs in their own <div>'s. This is fine for my project, YMMV

This helped me out a bunch, thanks!