You can connect using more than one device, but not at the same time.
The controller will pick up the first device it can find. If you have multiple devices in the room compatible - turn Bluetooth off for the devices you do not want to connect, only leaving the one available to be found and connected.
Equally - if you're brewing on multiple G30's - then pair them up one at a time. So, turn Bluetooth off all devices except the first one and turn on the right G30 and connect. Then turn on Bluetooth on the next device and turn the next G30 on and connect and continue like that.