While Windows 10 Mobile launch is near, Microsoft is polishing the OS with some tweaks and improvements.
WMPU reports, Microsoft has added one new feature on Phone app which allows the phone to vibrate when someone picks up your call. For example, you don’t have to keep your phone closure to ear, when you are calling someone and waiting for your call to be picked up.
However, it seems this feature is only available in Windows 10 Mobile build 10549.
SOURCE: WMPU