Not sure why the apps were retired - tech support often requires looking at the 'why' for an alert of being able to manage the alert (pause it) when you are not next to a computer. With the retirement (for whatever reason) of the app, you are forced to log in to the website from a mobile device - there is no 'web version' so trying to navigate your way around and having to slide the screen left and right is completely to try and find a check box or menu item is completely unusable.
Need a functional way to manage your Pingdom alerts via a mobile device . . . it can't be that difficult.