As of App version 7.0 your Body Scan's haptic feedback vibration can be turned on or off in the settings of your Withings App.

To toggle this setting, please perform the following steps:

1. Open the Withings App.
2. Tap the Devices Icon in the upper-right corner.
   
3. Find your Body Scan and tap All Settings.
4. Under 'Advanced Settings' tap the Scale Vibration setting.