Can an app access the contact list? If yes what class do I use? If not, would 4.0 allow that?
Have yet to try it, but I think the answer is yes.
https://developer.apple.com/iphone/library/documentation/ContactData/Conceptual/AddressBookProgrammingGuideforiPhone/200-QuickStart/QuickStart.html#//apple_ref/doc/uid/TP40007744-CH2-SW1
See AddressBook and AddressBookUI frameworks.