Nice Introduction to WLDF Watch/Notifications
By Ramkumar Menon-Oracle on Sep 30, 2011
James Bayer has a simple hands-on video on setting up WLDF watches and notifications in WLS.
WLDF enables you to dump diagnostic images or send out JMX/Email notifications when any metric of your interest crosses a configured threshold. There's more to it, but here is a good start that will catch your interest!