Have you any thoughts for extending this plugin to work with Fingbox? https://www.fing.io/
They must be doing something unusual that I don't know about (or had the time to do tons of testing) as it's ability to detect both Andriod and iOS Phones presence without break with accurate arrival and departure times is quite noteworthy - it hasn't made a mistake yet.
Right now I'm just getting email alerts for the devices I subscribe to when they go on/off (home/away), but it would be nice to do this properly with a professional plugin from yourself