The [<googa>http://www.akaipro.com/product/apc-mini |Akai APC Mini] </googa> is well suited for use as a Midi controller for Box Of Stops.
The large grid of 64 buttons can respond in Green, Yellow and Red, to show the different [[Bank|banks]] in Box Of Stops. And the nine sliders at the bottom can be assigned as volume controls for the banks and [[Master volume|master volume]]. For example, the ability to balance pedals is surprisingly useful.
For a cheaper Midi controller that also offers feedback lights, and sliders, please see the details about the [[Korg nanoKONTROL2]].
At a much simpler level, there is also the option of using the [[Status Board]] from The Pi Hut. This plugs directly into the [[Gpio controller button|Gpio connector]] on the Raspberry Pi.