The update is finished, and now Net Ping will let you ping a host continuously.
In the Settings, tick the box, and that will put the app in continuous mode.
Ping is only running while the app is visible on your phone. If you switch to a different app or go to the home screen, the ping is paused. The primary reason for this new behavior is because of the activity cycle (see a different blog entry here). In short, if ping isn't paused, you could lose control of the ping when you come back to the app.