The objective of this functionality is to determine that your are at home based on your phone connexion to your wifi network and use that information on your Home Center for example to switch off your alarm automatically when you are in and switch it On when you are out... Most of phones are impossible to be easily found as soon as they are on sleeping mode; therefore a simple ping won’t work. I’ve done this workaround with the help of a raspberry and fing which is a free powerful network too