I recently ran into an interesting problem working on putting support for the Windows Azure Access Control Service (ACS) into the Windows Azure iOS Toolkit.
It turns out that once you’ve gone through all of the ACS authentication process, a security token is generated. You need this token to authenticate yourself against ACS-bound web sites. However the ACS web site passes the token to you by calling window.external.Notify()
window.external.Notify("security-token-here");
While window.external.Notify is supported in Internet Explorer on the desktop and also in Windows Phone, it is not supported in iOS. Worse, while the WebView control on the Mac can call your Objective C code from JavaScript, the iOS UIWebView does not support this.
Another mechanism was needed. Here is how I solved it.