Keychain tracking (NFM?) options?

As part of my HA setup, I would like to find a near field device to attach to my families keychains so I can take action based on their entering or leaving the house. … since they don’t always carry phones and they don’t want to run any background apps on their phones anyway). I need to find both the keychain fob/device and a relatively inexpensive reader but not sure where to look (or what I’m looking for). Any thoughts?


I used an ESP32 board with this RFID tag reader: RDM6300 NFC/RFID — ESPHome (<$2 on AliExpress) and a few 125kHz RFID keychain fobs (<$0.50ea).

I buried it in the door frame of my front door. It switches the alarm on/off and locks/unlocks the door when the fob is held near the door frame. The key fobs aren’t writeable but I can tell which one was scanned. I can tell which key was scanned. Both by the home assistant tag event and ESPHome binary sensor for each fob.