I have been using as part of a portable setup, the Korg NanoKEY Studio. While I would not recommend this controller for “keys”, because of the click and switch feel of the keys itself, it extends the capabilities of Korg Gadget considerably. One of the best parts about using it is the Bluetooth capabilities. No cord at all, you simply turn it on and activate it in the Korg Gadget setup screen.
Very easy to use. Because it is properly mapped to all of the Korg Gadgets, there is nothing that you have to do to set it up. You simply activate it and it works!
The video above will give you a great intro into its use.