I am using Ruby on Rails for a project and I was searching for a similar tool like DebugKit in CakePHP, but for Rails and found RackBug. The both tools provide you with debug information, database queries, request details and so on.
Installing RackBug is easy. You can follow the steps in the readme file, provided with the gem. Just run
gem install rack-bug
Adding
config.middleware.use "Rack::Bug"
sometimes didn’t work. You have to change “Rack::Bug” -> ::Rack::Bug and add RackBug namespace in the environment/development.rb in your project. So you will have to have this
require 'rack/bug' config.middleware.use ::Rack::Bug
Don’t forget to open this url in your application to enable RackBug
http://RAILS_APP/__rack_bug__/bookmarklet.html
I wish you debugless debugging 
I am a Cakephp designer that is currently doing some perform in ruby on tracks and one thing i use a lot in cakephp is debug-kit which allows me to see many things within the website such as ask for details and variables available in the view.