Embedded RFID (radio frequency identification) tags for objects or containers and related systems and methods are disclosed that overcome problems existing with previous RFID tags. The RFID tags are embedded within recesses within the outer surfaces of objects or containers, such as within a metal valve flange for a metal container. The RFID tags can also be shaped and configured to fit within recesses so that the top surfaces of the RFID tags match the outer surfaces of the objects or containers. The embedded RFID tags can also be painted or otherwise disguised so that they are more difficult to identify. In addition, the RFID tags are preferably tamper resistant and can also use PSK (phase shift key) modulation. The embedded RFID tags described herein are particularly useful for tracking of liquid propane gas (LPG) containers and/or other types of containers or objects for holding hazardous materials.