UINavigationBar editable title?

You are able to set a custom view for your title.

titleView

A custom view displayed in the center of the navigation bar when the receiver is the top item.

@property(nonatomic, retain) UIView *titleView

Discussion

If this property value is nil, the navigation item’s title is displayed in the center of the navigation bar when the receiver is the top item. If you set this property to a custom title, it is displayed instead of the title. This property is ignored if leftBarButtonItem is not nil.

Custom views can contain buttons. Use the buttonWithType: method in UIButton class to add buttons to your custom view in the style of the navigation bar. Custom title views are centered on the navigation bar and may be resized to fit.

If you were to place a UITextField in your titleView you could give it a clearColor background and set it to have no border. Wala you have a UINavigationBar Title you can tap and edit.

Ryan's solution is exactly right. In case anyone is having trouble implementing it, here is some sample code that should get you going. Just paste it into ViewDidLoad on any class with a navigationController.

UITextField *textField = [[UITextField alloc]initWithFrame:CGRectMake(0, 0, 200, 22)];
textField.text = @"Insert Title Here";
textField.font = [UIFont boldSystemFontOfSize:19];
textField.textColor = [UIColor whiteColor];
textField.textAlignment = NSTextAlignmentCenter;
self.navigationItem.titleView = textField;

And if your project doesn't use ARC, make sure to release the textField like so:

UITextField *textField = [[[UITextField alloc]initWithFrame:CGRectMake(0, 0, 200, 22)]autorelease];

or like so:

[textField release];

Hope that helps.