I have been working on a project for a few months now that I am about to launch in a few weeks: Metrics Watch. What is it doing? Alerts for Google Analytics (and other metrics sources).
You want to know if your pageviews have gone above 5000 today as you might want to do something sooner than later? We can do that! You want to know if your bounce rate changed too much recently? There is possibly something wrong if your bounce rate has bumped by 10% in a week! We can tell you that, too!
We are going to focus on Google Analytics first, but we'll add more metrics sources.
Interested in being part of the beta or learn more at launch? Here you go: http://metrics.watch.
Enough words, here is a screenshot of what an email alert look like: