I'm looking for a way to tell the distance between an arduino and my phone.
Please share any direction / guidance.
Basically if I am (more specifically my phone) is more than 3 to 5 meters away from arduino, i'd like for it to do X.
I don't think there is any practical way to do that.
If you have a Bluetooth module on your Arduino you could try communicating with the phone and draw conclusions if the communication ceases. But there are so many things that interfere with wireless communication that it is not likely to be useful.
...R