metaWeblog.getRecentPosts is returning nothing in my iphone app

The XML-RPC has a filter, where you can add your custom methods:

function wpse60127_xmlrpc_methods( $methods )
{
    $methods['newWPSE60127Method'] = 'wpse60127_new_method';
    return $methods;
}
add_filter( 'xmlrpc_methods', 'wpse60127_xmlrpc_methods' );

Simply add your own methods there (core methods/functions) are also allowed.