By Raphael Satter WASHINGTON (Reuters) -Unidentified governments are surveilling smartphone users via their apps’ push notifications, a U.S. senator warned on Wednesday. In a letter to the Department of Justice, Senator Ron Wyden said foreign officials were demanding the data from Alphabet’s Google and Apple. Although details were sparse, the letter lays out yet another path by which governments can track smartphones. Apps of all kinds rely on push notifications to alert smartphone users to incoming messages, breaking news, and other updates. These are the audible “dings” or visual indicators …