Clarifruit's app supports a number of external devices using the Near Field Communication (NFC) or Bluetooth technology (depending on the device type) available on your mobile phone.
To connect a device, tap on the settings icon:
Choose the 'devices' option in the settings section:
Choose one of the devices listed:
Note that tapping on the information icon, will redirect you to the device manufacturer homepage. You may want to verify that the NFC or Bluetooth communication of your mobile device is activated.