Radio Frequency Proximity Detection Devices

A method comprising:

• transmitting, by a first radio frequency transceiver of a first device, a first signal;
• receiving, by the first radio frequency transceiver of the first device, a second signal in response to the first signal;
• determining a time value associated with the receiving of the second signal;
• determining that at least one of the time value or a distance value determined using the time value is less than or equal to a first threshold value, wherein the first threshold value is associated with the first device;
• and
• triggering a first output by a user interface component of the first device based on at least one of the time value or the distance value being less than or equal to the first threshold value.

A system comprising:

• a plurality of radio frequency identification (RFID) tags;
• an RFID reader configured to:
• receive data including a tag uniform identifier (UID) or class;
• interrogate and singulate the plurality of RFID tags in a reflective state, and
• transmit an instruction causing tags not associated with the received data to enter a non-reflective state;
• and
• a device comprising a transceiver and a user interface, the device configured to activate the user interface in response to receiving a signal reflected from an RFID tag in the reflective state.