Update 5/2012: Read our latest blog post about Continuous Deployment for Heroku Apps
We’re in the process of developing a Heroku Add-On to provide seamless Continuous Integration and Deployment of your Heroku app, using our test infrastructure to automatically run tests, manage results and actions to take on tests passing or failing.
After you enable the tddium heroku add-on and configure tddium to work with Heroku, Tddium will automatically run tests when you push changes to Heroku (or some other repo Tddium is watching, like github). You can configure Tddium to email tests results, or post them to Campfire. Tddium will even auto-deploy changes in one Heroku App to another, so you can use Continous Deployment without having to setup a CI server on your own.