PIM api is included in the latest version of WTK. You just need to select a checkbox o include it in your applications if you are using WTK.
WTK 2.3 is available here:
http://java.sun.com/products/sjwtoolkit/
And here are some examples using PIM api:
Reading/Modifying Native database of mobile device
http://www.java-tips.org/java-me-tips/midp/reading/modifying-native-database-of-mobile-device.html
How to create Events/Task/Reminder in mobile phone
http://www.java-tips.org/java-me-tips/midp/how-to-create-events/task/reminder-in-mobile-phone.html
How to find contacts from PhoneBook of mobile phone
http://www.java-tips.org/content/view/1379/62/