UISegmentedControl *segmentedControl = [[UISegmentedControl alloc] initWithItems:
											[NSArray arrayWithObjects:
											 [UIImage imageNamed:K_IMAGE_UPARROW],
											 [UIImage imageNamed:K_IMAGE_DOWNARROW],
											 nil]];
//[segmentedControl addTarget:self action:@selector(segmentAction:) forControlEvents:UIControlEventValueChanged];
segmentedControl.frame = CGRectMake(0, 0, 90, 30);
segmentedControl.segmentedControlStyle = UISegmentedControlStyleBar;
segmentedControl.momentary = YES;
	
UIBarButtonItem *segmentBarItem = [[UIBarButtonItem alloc] initWithCustomView:segmentedControl];
[segmentedControl release];
    
self.navigationItem.rightBarButtonItem = segmentBarItem;
[segmentBarItem release];

http://www.iphonedevsdk.com/forum/iphone-sdk-development/3057-uisegmentedcontrol-uinavigationitem.html

This works for me!

UISegmentedControl in UINavigationItem

Objective C