Sigmund is friendly clojure wrapper around the Hyperic SIGAR API http://www.hyperic.com/products/sigar. It can tell you all sorts of information about your currently executing process as well as the system that you are working on. It provides quite a bit more information than JMX:
os: information, processes, memory, swap, resource limits, uptime and logins.
cpu: information, per cpu and average usage.
jvm: runtime information for jvm.
filesystem: mounted devices, disk usage, filesystem properties and usage.
network: usage, bandwidth, gateways, interface, routes and connection status.
process: per process information for cpu, memory, environment, credentials, arguments and other information.