Drupal and high CPU usage

I just spent about an hour trying to figure out what went wrong with my apache that was causing the process to take up about 90% of the cpu time on my nifty linux server. In the log of one of my drupal instances i found that it was a call to a missing php page, from a module that wasn't quite properly installed. So it turns out that it's quite possible to chew up the bulk of your CPU time if you're not careful with drupal configurations, just as it is with any process capable of infinite loops or recursion.

I'm wondering if there's perhaps a tool that can monitor drupal module events marked on a graph of CPU usage. That would be very handy for troubleshooting problems... Maybe i should make one. although i'm a bit worried about how much CPU time that might use!