(JLN...just to draw your attention to Derrida's rejection of "the metaphysics of presence" in case you have not come across it yet. But be advised... he also rejected Buddhist "mindfulness"
Not sure how you can reject something that is obviously present. All mindfullness is is awareness of present moment without allowing the usual attachment to phenomena to occur. Such as reacting to sounds or smells or sensations of the body like pain or discomfort from sitting in a certain position.
It is not a perfect condition that everyone experiences, it is something that can be refined and honed or trained. A person who is less trained will hear noises and consider them distractions where as a person who has some training will not be bothered by any sounds at all, not even loud explosions. (if such an example were made)
It also goes beyond just this focusing of the mind on awareness. Mindfulness also is a method of "watching" or "observing" the states of the mind itself. If you are happy, being able to recognize it and not attach yourself to it. If you are sad or angry or depressed. Being able to be aware of these states and not become immersed within them.
Also it is attention to all activities of the body and thoughts as well. If you are thinking about something or day dreaming, you are so focused you can be aware that you are day dreaming where as an unpracticed person would be so caught up in the day dream they wouldn't even be aware that they were doing so.
Developing this skill of mindfulness actually empowers the individual because you can solve problems before they even occur or before they become more complex. They refer this to uprooting unwholesome thoughts before they become negative actions or speech phenomena. A method of preventing saying or thinking something that would result in karmas that would much rather have been avoided.
So even thought this explanation is long, mindfulness is common and practice and to denounce it's existence is only done by those who don't even understand the concept or how it is used as a tool.