Konpasu is a project mainly written in Ruby, it's free.
Drop-in Heroku/Compass integration
Tested on Heroku with Ruby 1.9.2, Rails 3.0.5, and Compass 0.10.6
To use, simply add: gem konpasu
to your Gemfile, and Heroku will automatically set up Rails to compile and serve your SASS stylesheets out of the tmp/ directory.