Amazon has long provided a service called CloudWatch for its AWS cloud services which can send a notification when an EC2 instance surpasses certain thresholds (such as excessive memory utilisation). A new enhancement to CloudWatch now allows IT managers to automatically stop or terminate an EC2 application when an alarm is sent.
As the blog post which announces the feature notes, this could be used to shut down instances which aren't actively being used, or to stop applications which develop a bug and begin consuming excessive resources. It's not an option everyone will need, but useful if you want to tightly control your AWS charges.
Amazon CloudWatch - Alarm Actions [Amazon Web Services Blog]