Mark Blunden and Adrian Escott described differential related key attacks on five and six rounds of KASUMI.
In 2005, agents from the U.S. Federal Bureau of Investigation publicly demonstrated the ability to do this with widely available software tools in about three minutes.
One approach to preventing related-key attacks is to design protocols and applications so that encryption keys will never have a simple relationship with each other.
Another, more conservative approach is to employ a cipher designed to prevent related-key attacks altogether, usually by incorporating a strong key schedule.
A newer version of Wi-Fi Protected Access, WPA2, uses the AES block cipher instead of RC4, in part for this reason.
There are related-key attacks against AES, but unlike those against RC4, they're far from practical to implement, and WPA2's key generation functions may provide some security against them.