Re Andy’s SeeVolution post, a similar tool that has some decent features is Chartbeat.

How both differentiate from say Google Analytics is by identifying ‘unusual’ behaviour on the site that requires instant action or optimisation. For example:

• Identifying an unusual high volume source of traffic  (from a blog, article, etc), and controlling that conversation or situation;
• Identifying instances of poor user experience (bounce rate, etc) from users arriving via high spend media placements, and optimising or changing the landing page;
• Identifying page load times and errors on a day when you know high volume is expected.