Know When You're On Localhost - WordPress

localhost.wordpress.php

<?php
function opubco_localhost() {
	// Do check for localhost IP (remove this if you want to ALWAYS display it)
	if ( '127.0.0.1' != $_SERVER['REMOTE_ADDR'] && '::1' != $_SERVER['REMOTE_ADDR'] ) {
		return;
	}
	if ( defined( 'WP_DEBUG' ) && WP_DEBUG == true ) {
		$debug = 'WP_DEBUG=ON';
	} else {
		$debug = 'WP_DEBUG=OFF';
	}
	echo '
		<div style="
			position: fixed;
			right: 10px;
			bottom: 10px;
			width: auto;
			padding: 0 8px;
			height: 22px;
			background: #ff0000;
			border-radius: 5px;
			box-shadow: 0 2px 5px 2px rgba(0,0,0,0.3);
			z-index: 99999999999999;

			font-family: sans-serif;
			font-size: 13px;
			line-height: 22px;
			color: #fff;
			font-weight: bold;
			text-align: center;
			text-shadow: 1px 1px 1px rgba(0,0,0,0.3);
		">' . php_uname( 'n' ) . ' ' . $debug . '</div>';
}
add_action( 'wp_footer', 'opubco_localhost' );
add_action( 'admin_footer', 'opubco_localhost' );
?>