Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 22831)
+++ wp-admin/includes/media.php	(working copy)
@@ -1498,6 +1498,11 @@
 	'multipart_params' => $post_params
 );
 
+// Multi-file uploading doesn't currently work in iOS Safari,
+// single-file allows the built-in camera to be used as source for images
+if ( wp_is_mobile() )
+	$plupload_init['multi_selection'] = false;
+
 $plupload_init = apply_filters( 'plupload_init', $plupload_init );
 
 ?>
Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 22831)
+++ wp-includes/functions.php	(working copy)
@@ -2273,8 +2273,11 @@
  * @param mixed $response Variable (usually an array or object) to encode as JSON, then print and die.
  */
 function wp_send_json( $response ) {
+	nocache_headers();
 	@header( 'Content-Type: application/json; charset=' . get_option( 'blog_charset' ) );
+
 	echo json_encode( $response );
+
 	if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
 		wp_die();
 	else
Index: wp-includes/js/media-models.js
===================================================================
--- wp-includes/js/media-models.js	(revision 22831)
+++ wp-includes/js/media-models.js	(working copy)
@@ -789,4 +789,9 @@
 		}
 	});
 
-}(jQuery));
\ No newline at end of file
+	// Clean up. Prevents mobile browsers caching
+	$(window).on('unload', function(){
+		window.wp = null;
+	});
+
+}(jQuery));
Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 22831)
+++ wp-includes/media.php	(working copy)
@@ -1254,6 +1254,11 @@
 		'multipart'           => true,
 		'urlstream_upload'    => true,
 	);
+	
+	// Multi-file uploading doesn't currently work in iOS Safari,
+	// single-file allows the built-in camera to be used as source for images
+	if ( wp_is_mobile() )
+		$defaults['multi_selection'] = false;
 
 	$defaults = apply_filters( 'plupload_default_settings', $defaults );