I'd like to hear your approaches for monitoring Linux instances running in EC2. I'm very accustomed to using Nagios to monitor all manner of aspects of a Web-based application's ecosystem, but its model doesn't seem to lend itself particularly well to machines that are fairly frequently destroyed and recreated. My EC2 instances are intermediated by RightScale, which has its own monitoring scheme that I'm not finding hugely useful -- though I do plan to look into their monitoring some more.
The instances in question run normal open-source stuff: MySQL, Apache, Passenger, Rails.
Many thanks in advance.