[Q] Galaxy Note 10.1 input device - button control or rotary control

Has anyone ever used an external device to control app functions? Bluetooth connection would be preferred but USB would be fine too. I really couldn't find any info on anything other than mice or keyboards. What I'm looking to do is have an extra form of programmable input for certain apps for an extra level of control. Specifically, I want to have something that will quickly allow me to change brush size, opacity, select different tools, etc in Sketchbook Pro. Something like the Contour ShuttleXpress would be perfect, but I couldn't find anything that would allow me to use it with Android.

3DConnexion SpaceNavigator and Griffin PowerMate looked good too but I couldn't find any support for Android for them either.

Am I missing something or am I out of luck to use any of these without some custom code? Are there any alternatives?

Thanks