I had an interesting glitch the other day. My wife's Alexa app wrongly decided she had left the house one day. So then when her iPhone's wifi went to sleep, Combined Presence decided that she was actually away from the house. I myself was actually away from the house at that time, so my rules started trying to lock all the doors and shut the garage. Unfortunately, my wife and kids were playing in the garage and driveway at the time, so to them, it seemed like the house was going crazy.
So now I'm using Combined Presence with 3 input sensors for each person:
- Alexa geofencing
- HomeKit geofencing
- iPhone Wifi Presence Sensor
I haven't had a problem since. The Alexa and HomeKit apps seem to use slightly different geofencing algorithms, so my home is that they won't be subject to the same error at the same time.