The Objective-C WebViewControllerDelegate from my blog entry An iOS5 Ready Native Web App Template http://www.bitwit.ca/blog/an-ios5-ready-native-web-app-template/

WebViewControllerDelegate.h

/**
* WebViewController is responsible for all
* messages that can be used in HTML
*/

@class WebViewController;
@interface WebViewControllerDelegate : NSObject <UINavigationControllerDelegate, UIImagePickerControllerDelegate>

@property (nonatomic, weak) WebViewController *webViewController;

/*
* Test alert from Objective-C
 */
-(void)message:(NSString *)name;

/* On successful picture selection, a base64 image
* is sent to the JS function processImage();
*/
-(void)takeCameraImage;
-(void)takeLibraryImage;

@end

WebViewControllerDelegate.m

#import "WebViewControllerDelegate.h"
#import "NSData+Base64.h"
#import "WebViewController.h"

@implementation WebViewControllerDelegate

@synthesize webViewController;

-(void)message:(NSString *)name
{
    //Showing a basic pop up alert
    
    NSString *message = [NSString stringWithFormat:
                         @"Your name is %@", name ];
    
    UIAlertView *alert = [[UIAlertView alloc] 
                          initWithTitle:@"Message From OBJ-C" 
                          message:message 
                          delegate:nil 
                          cancelButtonTitle:@"OK" 
                          otherButtonTitles:nil, nil];
    
    [alert show];
}

-(void)takeCameraImage
{
    if ( ![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] )
    {
        NSString *message = [NSString stringWithString:
                             @"Your device does not have a camera" ];

        UIAlertView *alert = [[UIAlertView alloc]
                              initWithTitle:@"No camera available"
                              message:message
                              delegate:nil
                              cancelButtonTitle:@"OK"
                              otherButtonTitles:nil, nil];

        [alert show];
        return;
    }

    // Set the UIImagePicker, set it to theCamer and set self as the delegate 
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
  imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
	imagePicker.delegate = self;
    
    // Present the image picker
	[webViewController presentModalViewController:imagePicker animated:YES];

}

-(void)takeLibraryImage
{
    // Set the UIImagePicker, set it to theCamer and set self as the delegate
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
	imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
	imagePicker.delegate = self;

    // Present the image picker
	[webViewController presentModalViewController:imagePicker animated:YES];

}

#pragma mark - Image Picker

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    //Get the Image
	UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
    
    //flatten it to NSData as a JPEG, low quality
    NSData *flatImage = UIImageJPEGRepresentation(image, 0.1f);
    
    // convert NSData to a base 64 encoded string
    // NSData+Base64 Category provided by Matt Gallagher
    // http://cocoawithlove.com/2009/06/base64-encoding-options-on-mac-and.html
    //
    NSString *image64 = [flatImage base64EncodedString];
    
    //process the image in javascript to be added to the page
    NSString *js = [NSString stringWithFormat: @"processImage('data:image/jpeg;base64,%@')", image64];
    [webViewController.webView stringByEvaluatingJavaScriptFromString:js];
    
    //dismiss the image picker
    [picker dismissModalViewControllerAnimated:YES];
	
}
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
    
    //cancel was hit inside of the camera view
    [picker dismissModalViewControllerAnimated:YES];
}
@end