Create a set of Mono.Cairo custom widgets for human device interface such as LCD dot matrix displays, LED bars, 7 segment displays, sensor meters, knobs, push buttons, etc.
To keep it simple the first control will be a circular meter, which can be reused to implement a circular knob.
Device
Since the widgets are intended to be used along an embedded device for demonstration purposes a GUI application will be a secondary project. It won't be a complicated interface just enough to show how to implement the circular meter widget with a live device that will send data over a serial port. It can be any microcontroller is just matter of specify the data format. At hand I have an MC9S12NE64 demo board, and of course the embedded software will be released. Check the hardware section for more information.