Resolvoing Shortened URL

[eluser]jmanpa[/eluser]
What approach might be best, using CI libraries or not, to take a url, say "http://bit.ly/somestuff" and somehow resolve and return the real url underneath. Assume the shortening service could be any, not just bit.ly.

Not knowing beforehand whether the url is shortened or not, the approach should not blow up if the source url was never shortened in the first place and is a valid url.

Thanks,
John