I use Pow for running my Rack Apps on my dev machine and love it. However, recently I needed to use Pry to debug some weird behaviour I was seeing in my app. Luckily, there's a gem called pry-remote which makes it dead easy to use Pry with Pow.
Add the gem to your Gemfile
gem 'pry-remote', group: :development
$ bundle install
Add a debug statement to your code
Finally, connect to your remote debugging session