I agree with everyone's recommendation to go with a Combined Presence solution. However, my presence only became rock solid when I finally added Life360 to the mix.
Originally I was only using the Mobile App + [UPDATED] iPhone WiFi Presence Sensor. Unfortunately my Android phone kept turning off WiFi when it slept. The presence sensor itself works really well, so this was a nuance of my hardware. I'm assuming the Life360 app itself is doing more active check-ins and making the presence status more accurate.
