How long are you using this? I tried arp once but devices didn't dissappear or showed in the table as expected. I force the Pi to refresh it's ARP-table by sending out one ping. Even if the phone is not responding to the ping, it does respond to ARP requests. If I try the ping, first thing the ...

You are right. I have now added one ping to force the Pi to refresh its ARP-table.

I have written a script for presence detection based on WiFi presence that also works for iPhone (ios 10.1.1). The script checks the ARP table (Address Resolution Protocol) of the Raspberry Pi for the presence of a phone. If the phone is in the same network as the Raspberry Pi, it shows up in the ...