Silent mode: no vibration only for third party apps (Hangouts, Whatsapp, ...)
I've noticed a strange behaviour on my iPhone. I have it in silent mode, with vibration on. The phone vibrates if I receive an iMessage, while it does not vibrate if I receive a notification from another messaging app like Google Hangouts or Whatsapp.
I am sure that both Hangouts and Whatsapp are set with all options checked in the Notifications menu, including "Sound".
What could be the reason? I want to be notified with vibration for every notification I receive both in silent and non-silent mode.
iPhone 4S, iOS 6.1.1, 16 GB