To allow Vertigo to asses his orientation on the vertical wall, we use a large potentiometer. The potentiometer must be linear and have a range as wide as possible (preferable 360°). On top of this, he has to be very flexible, so a simple small mass will be able to position the meter with the help of gravity.
Once more, use a 5V power supply. This allows a direct processing of the output signal by the microprocessor, without any extra electronics. The potentiometer signal is an analogue signal, so make sure it is hooked up to the correct pin of the microprocessor. Not every pin of the PIC has a converter to turns your analogue signal into a digital one you can easily manipulate in your software.