Uptimetry is an add-on for monitoring your app's vital resources. Think of it as real-time view testing. Make sure your sign up page is displaying correctly by confirming HTTP 200 OK and matching content in the response via CSS selector or XPath. Receive email when your page is not rendering as designed.
Uptimetry can be attached to a Heroku application via the CLI:
A list of all plans available can be found at http://addons.heroku.com/uptimetry.