Don't like to be the buzz kill, but the app isn't actually doing any calibration, its fake. It may try to simulate a screen calibration by turning up the brightness, but you can't actually 1 click calibrate any monitor.
Calibration requires adjusting post processing features, RGB ratios, gamma etc...
This can only be done manually, on a screen by screen basis, using calibration images and videos as guides, whilst the user makes the changes based on how those images appear, as the same image may appear different on different screens, no app or software can detect what those differences are unless your using a physical calibration tool which is put on the screen itself to measure how the screen is outputing certain images and colours.
There is no Google api to allow any apps to do anything of the sort. No apps actually have the permissions to change the calibration of the screen, other than the simple RGB adjustments in settings, which isn't close to enough to actually call it a calibration anyway.
