use RFID ( or what else? ) for a broad distance measurement in 1-2 meter wide area
The closest you could come to what you want would be a reader with a transmitter which has variable output power (and I don't know of any that do). If you step through different power levels and keep track of which items "disappear", you might get a rough idea of range. That said, it would not be accurate. It would depend on geometry and shielding (inadvertent or otherwise).