Be able to start a call on WhatsApp via a mobile device that is connected to the portal and is currently on the same WiFi network. Then be able to push that call to the portal screen of your choice (if you have more than 1 in the house) so you can continue the call but have your hands free to do things.

Also be able to do it the other way round, i.e. make a WhatsApp call on the portal and push the call to the mobile device so people can leave the house and still be on a call.