From Axe-Fx II Wiki
Forum member and programmer AlGrenadine has created a super handy editor for the Axe-Fx II and AX8: FracPad. It provides all the tools to edit and manage presets, blocks etc, on a table, smartphone or computer. More information on the forum
Versions for Windows and OS X can be downloaded for free.
This requires a compatible USB adapter, called "USB OTG". This works with the AX8 and Axe-Fx II models.
No reliable wireless solution (Bluetooth) has been found yet.
Axe-Fx II and iOS (wired and wireless)
A wired connection requires a MIDI-to-USB interface, because the USB port on the Axe-Fx II doesn't operate as USB host. Use a 3rd party iOS MIDI interface, such as iRig2 MIDI, or a general purpose USB-MIDI interface like Roland's UM-One in conjunction with the "USB camera adapter" for Apple devices.
A wireless connection can be established through Bluetooth. The Yamaha MD-BT01 interface is recommended. It connects to the MIDI IN and OUT ports on the Axe-Fx II. Launch the app "Midimittr" (AppStore), followed by FracPad.
AX8 and iOS (wired and wireless)
A wired connection requires an USB connection, because the AX8 doesn't support editing through MIDI. Use the "USB camera adapter" for Apple devices.
A wireless connection can be established through Bluetooth. Use Yamaha's UD-BT01 interface and verify that it runs firmware 1.03 or later (run the Yamaha UD/MD utility, available in the US / Canadian app store). Launch the app "Midimittr" (AppStore) to enable the communication, followed by launching FracPad.
Bluetooth wireless connections between Axe-Fx II or AX8 and iOS devices
Bluetooth LE (Low Energy) is required, so make sure that your iOS device handles Bluetooth 4.0+. This requires at least an iPad 3 or iPhone 4s (source).
Bluetooth operations are not officially supported, so use at your own risk.