Cocoa method to return a list of all letters in the current locale's alphabet?

I'm currently trying to implement a UITableView with a delegate and data source that replicates, as closely as possible, the functionality found the ABAddressBookUI framework's ABPeoplePickerNavigationController class, but with the added ability to select multiple contacts at once (as indicated by adding/removing an accessory view to the appropriate UITableViewCell).

Everything is working fine, with the exception of providing localized "section index titles" (the letters that appear in the scroll overlay to the right of the screen) for the UITableView, as should be returned by the data source method:<