With global flight coming out, I find that many of us will be putting out heavies on autopilot for our long voyages around the world. I thought it would be a good idea to have ATC vibrate notifications when ATC contacts you specifically so you know that message was for you. Many of us will probably put out phones/tablets down and let autopilot do most of the flying, so we are bound to zone out every now and then, so it would be nice to have that little vibrate to remind and tell you that ATC command was for you.
The vibrate function can also be used to give extra emphasis to pilots not listening to instructions or to tell them to check help pages. (Thanks to @PlanesForLife for this idea).
Also vibrate notifications would only work above a certain FL to avoid your device from vibrating while performing a manual landing.