Quick Arduino Project

I need to attach a potentiometer and button to an Android tablet (Samsung Tab A 8") to control an application. The freelances should be able to select an appropriate low-power device (Arduino Nano?), set up to pass rotation and button presses to the tablet, much like a volume control/mute USB device.

The tablet will be attached to a USB hub to accept data from the pot as well as control another USB device. Bonus points for devising a method by which the tablet may be charged/powered through the same USB connection.