There is xbee sx pro there is aes-256 encryption that I placed away from my house. I use this as a relay. it is API mode and router mode. What level of security is this? If someone gains physical access to it, can they listen to the communication?
Yes, if someone gains physical access to your remote device, they do have the ability to send data on the network. They can also receive data if the data is sent to its 64 bit address or as a Broadcast packet.
It should be noted that if you enable the special security functions, unless data is sent directly to it, it will be secure.