This is an RFE for providing a way to determine from the hadoop command line whether a jobtracker is idle. One possibility is to have something like hadoop jobtracker -idle <time>. Hadoop would return true (maybe via some stdout output) if the jobtracker had no work to do (jobs running / prepared) since <time> seconds, false otherwise.
This would be useful for management / provisioning systems like Hadoop-On-Demand
HADOOP-1301, which can then deallocate the idle, provisioned clusters automatically, and release resources.