When one understands human nature and 'know thyself' [Socrates] thoroughly one will come to understand why 'mindfulness-proper' is essential for any human being to function optimally.
"Mindfulness" is central to Buddhism but it is not a specifically patented Buddhist element. Rather it is a natural process and procedure that is common to all human beings, just like the necessity to eat a balanced diet to be healthy.
The confusions, problems and abuses arising from practitioners and critics are due to the constraint of semantics in representing the true processes of mindfulness. Generally it is always the insufficient but only available English or any translated 'terms' that set off the wrong perception.
For example, 'Focus on the NOW or PRESENT' will spontaneously lead the many lay people to interpret the term in accordance to their habituated meaning and thus strayed off from the intended meaning as used in 'mindfulness.' They will interpret this as focus on the present and forget about the past and future.
Another related case is the example the translating of the sophisticated Pali term 'Dukkha' as 'sufferings' which led to many to wrong perceptions and condemnations by critics on this significant core principle of Buddhism.
Thus to understand 'what is mindfulness' truthfully one need to get behind the semantics to the actual machinery and processes that warrant the need for 'mindfulness' and how 'mindfulness' actually work.
To have an efficient understand of the detailed processes one need to have a wide range of knowledge on human nature down to its neural basis within neuroscience.
The main feature of mindfulness is where one is highly mindful of what is needed to perform optimally within the present moment and one is fully
engage with reality and aware of what is past, present and future. This is a very common feature of sport champions where their mind is fully focused on the game and their 'eyes are on the ball' all the time but not to the extent they will not run away if there is a bomb threat in their midst.
To cultivate a sound and efficient state of 'mindfulness,' there are various practices to do it and the basic starting point is the focus on the 'breathing.' Whilst this basic process do provide immediate benefits to the practitioner, one need to know this resulting positive state is not its final objective.
The other intermediate progress towards a 'state of mindfulness' is the modulation of the 'Ruminating Loop' that end up with 'noises' and 'chatters' which hinder optimality of one's well being. This is control of the 'Ruminating Loop' is very critical as 'noises' can lead one to serious psychological detriments/damages in life.
Here is one useful guide to mindfulness from the secular perspective;
http://www.amazon.com/Full-Catastrop.../dp/0345536932