As noted in the comments below, this is no longer possible in iOS version 5.1 and after.
If you are on iOS 5.0, the following applies:
This is now possible in iOS 5 using the 'prefs:' url scheme. It works from a web page or from an app.
example urls:
prefs:root=General
prefs:root=General&path=Network
sample usage:
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=General"]]
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=General&path=Network"]]
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