The “Gmail” they refer to is not an app. It is Gmail’s web view in the iPhone Safari mobile browser. The connection bar is an on-demand secondary status bar that lets iPhone Gmail users know, for example, the status of a message as it is being sent, when checks for new email are being made, and when the iPhone (or iPod touch) is offline.
Google’s goal is to convince users of its services that native applications are unnecessary if a web app can look, feel, and act like a native piece of softwre. This, of corse, is to prepare their comfort level for Chrome OS based keyboarded computers as well as moving people away from native apps on smartphones and tablets.