Data Fence is a personal security tool to monitor access to your data, alerting you when hackers, government spies, or overly curious co-workers access your personal files. It can also be fun just to discover all the activity that occurs behind the scenes such as when you create a document or plug in a USB thumb drive.
PS Logger supplements the information collected by Apple's BSM audit system. Apple's BSM audit system is a fantastic audit system, but BSM has one glaring flaw. If a process existed before a BSM audit file is created (say /usr/local/fubar is running as process 392), there is no evidence in the in the audit file that the fubar program is running. PS Logger helps address this.