+1 to monit. I have an app that does a lot of scraping via Selenium, headless using xvfb and Firefox. If the Selenium scripts fail, Firefox never closes. On an EC2 micro instance, it doesn't take long before 40MB+ FF processes kill other things, like Tomcat (which runs my queue processor). I use monit to watch the root URL, and when it fails, it fires off a handful of scripts that restart the various pieces of the application.