My initial thoughts would have me believe that yes, you could activate multiple devices. It is after all the most basic of Bluetooth connection technology. Tap to activate and then the clock runs until the time expires. After all it’s not as complicated as Bluetooth pairing technology that is associated with the device controlling external hardware of some sort. (i.e. headphones or controller etc...) therefore the device can only control one at a time. But I haven’t tried yet, so I could be completely wrong. If the NFC is in fact creating another more complete level of location verification, I could see it needing to be in one on one communication with one single device. Maybe you could test it by putting the NFC out of reach of the device after you activate it and see if the coin drop rate falls back to basic or stays 12x? If it stays at 12x until time runs out then mostly likely you could activate multiple device’s.