You can download the second version of Jon's KM here https://communities.bmc.com/communities/docs/DOC-18793
(it uses the '/uptUptime' variable) or you can create you own version of KM, copy it to $PATROL_HOME/lib/knowledge of PA. Then, you need add '<NameOfYourKM>.km' to the agent configuration variable /AgentSetup/preloadedKMs.
That's all! After that your KM will appear in the PCO
By "chance" the newest version of UNIX KM includes a new parameter:
A new parameter, SystemUpTime, has been added under the UNIX_OS application class. This parameter reports the time (in seconds) for which the system has been up and running. This parameter can be used to monitor the up-time Service Level Agreement (SLA).