I have a couple of things automated in my room (fan, lights etc) using a server running on Rapsberry Pi 2 and relays.
Now I would like to implement a system to automatically detect when I am in the range of the Raspberry Pi, namely about 4-5 meters. Using a portable device such as a bracelet or a small thing attached to my clothes is what I would like and then the reader would somehow detect when I am around.
Long range RFID tags seem to be an interesting option, but I couldn't find a good solution that is compatible with RPi... and also I am not sure if it is safe to use such an antenna in my room.
I am not sure about bluetooth devices that would somehow automatically connect when I am around the RPi either, but I think that the device that will be attached to me won't be passive anymore.
Also, using my phone which automatically joins the wifi network would be an option, but I don't take my phone with me always and the router has quite a long range.
What is the best and safe way to have a passive device with me that would trigger my presence to the RPi?