Just recently we've noticed that calling [[UIApplication sharedApplication] openURL:url] with a tel: URI containing # or * characters is now permitted to be dialed in iOS 5.1.
e.g. NSURL *url = [NSURL URLWithString:@"tel:15555551212,,1234#"];
The documentation doesn't appear to have been updated to indicate that this is now allowed. It still doesn't work in iOS 4.x. We're testing to see when this changed. Does anyone know if Apple has officially changed its policy on dialing these characters from an app?