Open-monitoring meditation versus doing nothing

In psychology, there is a form of meditation called 'open-monitoring', which involves paying non-judgmental awareness to everything that arises in the present moment. I have heard, and read, that Buddhism typically advises one to have some experience with concentrative meditations before engaging in such open meditations. Is it necessary to have some experienced with focused attention in order to practice more objectless meditations? Is there a big difference between sitting on the cushion doing nothing, and practicing an open type of meditation? How is the concentration required?