Wonderfully smart readers ... I need to pick your brains.

We've been using Pingdom for years to track our sites. I love it. When sites go down it sends out an automatic email, SMS and even a message via an iPhone app.

When our servers go down, we know.

However, that's not the same thing as saying when our sites go down, we know.

This weekend a site was hit by a session error and that bought the site down. All a visitor could see was a MySQL error and the message "please repair the database". Because the server was still responding, Pingdom thought the site was up and so didn't tell us about the problem.

Any ideas on how we can get around this? How can we get notified even when our server is active but our site is throwing out errors?