My post Generating an AuthToken for SwitchUser demonstrates how to acquire and expire PeopleSoft authentication tokens. Using this approach, you could hook any custom application into the PeopleSoft security model, allowing PeopleSoft to manage security for many of your custom enterprise applications. Continuous token (ticket) validation could be implemented through a very simple web service that calls SwitchUser and returns the result. If
true, then the token is valid.
Really, if you are interested in a centeralized, integrated security solution, then you should speak with your Oracle rep about Oracle's Identity Management Suite.