Technology

What technology would allow me to send basic information to a receiver and gauge how far away it is?

My original idea was to use RFID tags but they dont allow me to gauge the distance. Is there any other technology that works in the same way but would show me the distance?

Public Comments

1. use radio frequency the received power decreases with increase in distance at the transmitter callibrate it to transmit signals at a constant power level at the receiver use two circuits one to receive the data other to calculate the received power level or try bluetooth but i dont know how you can calculate the distance . the bluetooth system will be integrated