Save custom field with editor

Hi,

I needed custom field with editor, so I use this code to achive that

global $post;
  $mobile_content = esc_attr(stripslashes(get_post_meta($post->ID, '_page_mobile_content', true) ));
  wp_editor($mobile_content,'mobilecontent');

but there is a problem. How could I save this to DB ( I have some other custom fields, but there are just inputs, so I can set them tag name)? I hnadle the saving procedure of my custom fields in my own function (creating metas or deleting them), but how can I save there an output from the editor, which creates an iframe with whole HTMl structure in it?
I get the values this way $_POST['mobile_page_content'], but how can I get the text from iframe?

Thanks