The instance_accountant gem is designed to be used to account for hourly resource consumption, such as EC2 instances, using Subledger, the double-entry accounting API. It can account for both cost (amount owed to AWS) as well as price (amount owed to instance owner). If you run hourly-billed instances for yourself, or for others, and want real-time usage information for yourself, and for those paying you for the instance, then this gem is for you. :-) instance_accountant keeps state in an "hourfile" that contains the timestamp of the last hour accounted for. It is intended to be run in --daemon mode at startup. It makes no effort to account for instance time when it is not running, so it's important to run it immediately upon startup, and to make sure that it is always running.