Long range RFID or other sensor

I might as well state my idea here so you get an idea of what I'm trying to do. I was looking at creating a quadcopter that would follow / track an RFID tag and potentially report its position to my phone. So the distance could be pretty far or relatively close. I suppose I'm looking for max possible. I have been somewhat distracted with another idea at the moment, but maybe if this is viable for me I may come back to it