You might also want to check out a library I released at iPhoneDevCamp — OpenFlow.
http://apparentlogic.com/openflow
It is all core animation-based, so it’s easy to understand and customize to your needs. AFOpenFlowView is a subclass of UIView.
I included a demo application, and check out the blog entry on my personal website for a bit more information about its use. fajkowski.com
Drop me a line if you have any questions or comments!
-Alex