there are two ways to get the IP address of someone who visits your site...
either look in the server log files (work required = 0).
or write a php script like this
$ip = $_SERVER['REMOTE_ADDR'];
$to = "your email"
mail($to, 'visitor IP address', $ip);
you can condense that into a single line if you like
<?php mail('email@example.com', 'visitor IP address', $_SERVER['REMOTE_ADDR']); ?>