Using the drones WiFi to call out to your devices and their responses include distance. all a drone would need to do is do fly the perimeter of your house making multiple callouts and then it would be able to make a fairly accurate guess where everything is based on all the TOF calls.

Your router is capable of the same thing but it doesn't tend to move. Wifi triangulation happens in lots of places. Casinos and even in big box public stores like Walmart and Target. They aren't using drones to track you, instead use their multiple antenna's to see which area's of the store you visit.