New Relic

New Relic is a huge tool, both in terms of what it covers and the impact it can have on your business. Built around the idea of tracking and making sense of software analytics, New Relic allows you to get a more comprehensive feel for how your customers are interacting with your website. From tracking for the web and mobile through to server-side monitoring and synthetics (which allow you to run artificial tests through various elements of your site data), New Relic gives you power-grade tools to start identifying ways you can improve your results with a view to delivering actionable insights.

http://newrelic.com/