Is there anything like RFID that can work in a 1 to 3 meter range while maintaining a small footprint on the detected object side? Like something close to the size of a quarter?
I'm wanting to detect the presence of something at a range of 2 to 3 meters, but I want it small enough to easily and comfortably go on a key ring that goes in my pocket. It seems like the small RFID tags that are the ideal size, are usually limited to about 10mm, much to short for my application. Any type of RF device that I've seen seems to big for my goal and also I was hoping there was something like passive RFID tags that didn't require any sort of power.
I know some cars have features now that detect the key inside the car and won't let you lock the doors, does anyone know what method those devices use? Those are probably battery powered I imagine since I'm sure it's something in the Key FOB transmitting a signal, but whatever it is, is low enough power usage to not need battery replacements for years. I'd prefer not to have another key FOB sized object on my key ring, one key FOB is enough lol.