Works just fine. Some Androids also go to sleep so the arping is needed for those as well. You may need to tune it a little by adjusting the retry, timeout, and refresh fields on the Thing.
IFTTT only works with cloud services.
It’s been recommended many times. Given how well the Network binding works and all the other options, I’m not sure I would support adding this feature to the Android app.
That is correct, though if you want to be away for more than 5 minutes before going to “away” you will need Rules. See Generic Presence Detection.
How log do you wait? This binding, much like your original script, only checks every so often. That is what the refresh field controls, how often it attempts to ping the phone.
This is where the refresh and retry fields may need to be adjusted. There have been many threads on this forum discussing the best values for these fields for iPhone. I can’t find them right now though but perhaps someone can post a link.
That isn’t how OH works. You have an Item that represents whether the phone is present or not (i.e. online)/. You have another Item that represents whether the door is opened or closed.
If you want to do something only when the door opens and your phone is present you need a Rule.
I don’t have much else to offer and it seems lots of knowledgeable users are providing help.