If they're using Home Assistant then it's pretty straightforward. You can either have the devices report back their location and update based on a Geofence or you can check and see if everyone's on the wifi or not

Since we're an iPhone family I use iCloud3 in HomeAssistant to track our devices. After setting that up and associating the phones with people in HA it was just a matter of creating triggers based on us entering the home zone:

alias: Somebody Arrives Home
trigger:
  - platform: zone
    entity_id: person.jack
    zone: zone.home
    event: enter
  - platform: zone
    entity_id: person.jill
    zone: zone.home
    event: enter

We live at the end of a dead-end, so I set up the home zone to extend down the road a bit. That gives iCloud3 enough time to figure out we're home and trigger the automation in HA while we're still approaching. I combine the above with a check to see if it's roughly sunset to sunrise, and if it is then turn on the outdoor lights.

For doing things like turning off the lights when nobody is home, I have a similar trigger for everybody leaving the home zone, followed by a conditional that verifies everybody is away:

condition:
  - condition: or
    conditions:
      - condition: template
        value_template: >-
          {{ states('person.jack') != 'home' and states('person.jill') !=  'home'  }}