To make an app that will simulate on the screen a balance wheel of a Swiss watch oscillating at 5,5.5 and 6 beats per second. A slider to alter the speed with a readout of beats per hour and a level to make sure the device is flat. This needs to be extremely accurate preferably controlled by the system clock. Will also need to be able to expand and shrink the size of the image.
How this will work is that a real balance will be suspended above the image by its hairspring with the pivot of the balance resting on the screen over the simulator. The real balance will be spun so it starts to oscillate. You then alter the slider on the app until they are both running in sync with each other and then you can read off the speed at which the real balance is running at and adjust as required.
This is called vibrating a hairspring.