Is there any script or CMS exist with which I will able to make a site like http://whatismyipaddress.com
You don't need a specific CMS for a site like that.... You need only a small php code to show the ip for a visitor.
Ah... I see. I thought it's full-blown script. I got this small script somewhere... http://www.wallpaperama.com/forums/how-to-display-ip-address-php-script-code-function-from-visitor-user-t399.html Code (markup):
Look what I've found here http://www.wp-geolocation.com/ Code (markup): Now, what I'm going to add is a map... but how, which plugin for wordpress?
If you have the IP Address, you can give some details to the visitors. It is simple, you can use a simple API where you can send them the ip in the url and get the resutls back that you show onto your website. Check this API: http://www.ipgp.net/ip-address-geolocation-api/