// Remove Site Header on Handhelds (Tablets & Mobiles)
add_action( 'genesis_before_header', 'sk_remove_header_handhelds' );
function sk_remove_header_handhelds() {

	// if this is not a mobile device, abort
	if ( ! wp_is_mobile() ) {
		return;
	}

	remove_action( 'genesis_header', 'genesis_header_markup_open', 5 );
	remove_action( 'genesis_header', 'genesis_do_header' );
	remove_action( 'genesis_header', 'genesis_header_markup_close', 15 );

}