Does anyone have iPad popover examples?

Well without going into full detail, UIPopoverView is pretty straight forward.

Here's a simple example.

Header:

@interface MyCustomPicker : NSObject <UIPopoverControllerDelegate, UINavigationControllerDelegate>
{
    UIView* view;  // the base view passed in from the custom init function below
    UIPopoverController* popOver;
}

// this is passed in the view created inside http://AppController.mm,  
// I'll leave it as an exercise to the reader as to where to create this class in order to get that variable. 
- (id)initWithView:(UIView*)appView;  

@end

I'm assuming you understand the basics of the language so I won't bore you with the entire implementation:

// this converts a Unity GUI Rect to a CGRect for the purposes of pointing at the button you clicked on assuming iPad resolution
- (CGRect)GetMuxedRect:(CGRect)portraitRect
{
    switch( [[UIApplication sharedApplication] statusBarOrientation] )
    {
        case UIInterfaceOrientationPortrait:
            return portraitRect;
        case UIInterfaceOrientationPortraitUpsideDown:
            return CGRectMake( 768 - portraitRect.origin.x - portraitRect.size.width, 1024 - portraitRect.origin.y - portraitRect.size.height, portraitRect.size.width, portraitRect.size.height );
        case UIInterfaceOrientationLandscapeLeft:
            return CGRectMake( portraitRect.origin.y, 1024 - portraitRect.origin.x - portraitRect.size.width, portraitRect.size.height, portraitRect.size.width );
        case UIInterfaceOrientationLandscapeRight:
            return CGRectMake( portraitRect.origin.y - portraitRect.size.height, portraitRect.origin.x, portraitRect.size.height, portraitRect.size.width );
        default:
            return portraitRect;
    }
}

// call this somehow from your C# to Obj-C code bridge.  There are several ways to do this
- (void)OpenViewInPopover
{
    // You can replace this with something else, like maybe UIImagePickerController
    MyCustomViewController* vc = [[[MyCustomViewController alloc] initWithNibName:@"MyCustomViewController" bundle:nil] autorelease];  
    vc.delegate = self; // setup code for your embedded view controller

    self.popOver = [[[UIPopoverController alloc] initWithContentViewController:vc] autorelease];
    popOver.delegate = self;
    [popOver setPopoverContentSize:vc.view.frame.size]; // for your own custom views you'll want this line.


    // in this example, I have a GUI.Button with rect( 5, 384, 100, 40 ) somewhere on screen.  If you have a 3D GUI or something that doesn't use Unity GUI, you'll have to find your own solution for figuring out how to put the arrow pointing the right place.
    [popOver presentPopoverFromRect:[self GetMuxedRect:CGRectMake( 5, 384, 100, 40 )] inView:view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES]; 
}

// UIPopOverView delegate methods
- (void)popoverControllerDidDismissPopover:(UIPopoverController*)popoverController
{
    // you might want to do something else here, like sending a unity message to change something from what was in the view
    self.popOver = nil;
}

The real work is going to be figuring out how to send information back and forth between your game and the view controller you put in the UIPopOverView. For example, for a simple toggle switch, you'll probably want to call a native code function that sets a bool on your view whenever it changes in game. Likewise, when the bool changes in native code you'll want to send a message back downwards to notify the game.

For sending messages from Unity into the view controller, the pattern I use is to create the MyCustomPicker object on startup, and do a simple singleton style pattern. So outside the @implementation block do something like this:

// static instance that gets set in init
MyCustomPicker* selfCustomPicker;

// this is a native function you'd bind to and call from Unity script
void OpenCustomPicker()
{
    [selfCustomPicker OpenViewInPopover];
}

Also, if you have a view controller with something like a "done" button (i.e. UIImagePickerController), that done button callback should call the -(void)dismissPopoverAnimated:(BOOL)animated function on your stored UIPopOverView.