Yup, BLE can transmit data without pairing. That's how AirTags and the like work. Basically, BLE is designed for lightweight sensors that periodically wake up

Yup, BLE can transmit data without pairing. That's how AirTags and the like work. Basically, BLE is designed for lightweight sensors that periodically wake up and blindly transmit their data. It doesn't know or care if anyone receives. The amount of data is small and necessarily unencrypted. Throughput is also very low. For bidirectional communication, you might be able to do the reverse: have your device transmit these blind BLE packets, but I don't know offhand if that's supported in Android. There may be other ways, like packing some data into an advertisement query or something. Again I'm not sure how well it's supported in Android, but under Windows you can silently establish a connection with an unsecured BLE device without user interaction. You don't actually pair to BLE devices most of the time, it's a different mechanism. And again this comes without encryption, but there's ways around that.