I believe the packages you are looking for are called rstatd and rstat-client in ubuntu. You need to have the rstatd package installed on the remote machines so you can then run rup (from rstat-client) command on them. Depending on which distro you are using, you may need to grab the source from the rstatd sourceforge page.
http://rstatd.sourceforge.net/http://packages.ubuntu.com/hardy/net/rstatdhttp://packages.ubuntu.com/dapper/net/rstat-clientCheers,
~KC