What would be the easiest way for my control system built around multiple ESP8266 modules to detect whether i am home or not. There are 3 things i never leave my house without: my keys, my wallet and my mobile phone. My keys are in keylock when i am home, my wallet is in a drawer and my mobile phone is near me generaly. Now i thought about simply using wifi or bluetooth signal meaning when i am connected to home wifi or system can detect me through bluetooth. But the thing is i generaly have all those things turned off on mobile phone, meaning wifi, bluetooth, data and location are all turned off unless i need them. So next thing i though about is to simply make a lever and if i hang my keys there it means i am home. But i like to keep my keys in keyhole. So, is there a way to have some passive keychain or maybe a card of sorts in wallet and then sensor somewhere in the apartment that will either detect it or not. I am looking for a solution as simple as possible that will not make me do something special everytime i leave or come home, otherwise i would just use a button and press it when i come home or leave.