nmap it is possible to check if an iPhone is available in the network even so.
At least execute 3 times following:
sudo nmap -PO -sU -p5353 -Pn <ip-address> | grep "1 host up" | wc -l
The best way is to regularly do this UDP ping and then e.g. if the phone doesn't reply even after
x minutes it is set to be away. This is handy for presence detection in smart homes.