To control your EFOY COMFORT with the free EFOY app, you will require the latest version of the app, the most recent firmware for your fuel cell and the EFOY Bluetooth adapter. The EFOY adapter communicates with the EFOY app via Bluetooth once connected to your EFOY COMFORT and sends you all important data, directly onto your mobile device. The EFOY Bluetooth adapter is compatible with every EFOY COMFORT fuel cell.