ScreenReact is described as 'displays patterns to test the picture of your LCD. E.g. contrast, sharpness'. There are three alternatives to ScreenReact for a variety of platforms, including Windows, BSD, Linux, Mac and SDL. The best alternative is Nokia Monitor Test, which is free. Other great apps like ScreenReact are lcdtest (Free, Open Source) and Screentest (Free, Open Source).
lcdtest is a utility to display LCD monitor test patterns. It may be useful for adjusting the pixel clock frequency and phase on LCD monitors when using analogue inputs, and for finding pixels that are stuck on or off.