Ambient Backscatter

I am looking into various RFID tags, RF transceivers, and beacon technology. Both active and passive rfid tags utilize taking in the signal from the locating device transmitter, but the passive mechanism is interesting to me in that it has no power at all of its own. It uses only the signal it gets when a transceiver is within proximity and sweeping  to find receivers. This signal’s backscatter is all that is required to allow the receiver to send its data to the transmitter.

With _ambient_ backscatter, such devices that can ‘wake up’ and send data, are powered not by specific transmitters or devices, but by the energy waves already in the air around us such as tv, radio, and cellular waves.

This means circuit sizes can be very small indeed, as small as 1sq. mm., and they can handle simple data, small sets of data with differences for indoor and outdoor,

I would like to monitor how much signal strength is around me and perhaps find out or deduce what objects are producing it.