I've checked in the SGAccountAlertView I made. I added it to SGUICatalogue so you can see how to use it.

The reason why you can't do this kind of thing with a modal view controller is that say a web request happens in the background and there is a problem and they need to enter account info, you would never know which view controller to present the modal one from. And if you do it on the wrong one you get a blank white screen - I tried trying to figure out which child of the tab controller is active but it just wouldn't work. So with this alert view design it can pop up no matter what the user is up to.

Btw I copied the idea from the App Store it does the same thing.