How tablet can find out that one or more phones aren't home

[jurkov]

My tablet (sm-t111, Android 4.4, Automagic) is a smart remote. I use it to remote my lighting system (Philips Hue). Everything is ok.

But I want to use my smartphone (S5, Android 7.1.2, Automagic)) as "a key" and S3 (Android 5, Automagic)

When I come home I want my tablet to "catch" my smartphone to turn lights. And when I left my home I want my tablet to "catch" this state and turn off the lights.

Problems:
There are two people with smartphones.
When we left home we don't internet accsses so I need in order to my tablet find out that nobody is home and turn off the lights.

Bluetooth?
Wifi?

[Martin]

Hi,

You could configure your WiFi access point to always use the same IP address for your phones and then use the condition Host Reachable on your tablet to periodically check if the phones are available.

Regards,
Martin