Question How to find out ISP from external IP address

[wingers]

Does anyone know how I could get my app to show the ISP of the machine it is running on, I can get internal and external IP addresses, just need to know if possible and how to look up ISP from this information

Some websites manage to do this such as Danasoft IP and City Sign Widget - For Myspace Layouts and Backgrounds, Forum Signatures, Blogs so I assume it must be somehow possible

Thanks in advance