Mindfulness is to be aware of happenings (reality of present moment) all the time in your physical boundary and even outside. The awareness of the interaction of outside objects with/within physical boundaries is done with Mindfulness. This is a very simple crude definition.
Mindfulness is related to the constantly changing body and mind sensations, they are like a bubble, just one touch and they pop...how can you take them seriously? From the Phena Sutta
Almost there, you just need to see the flux of phenomena as it really is without the overlay of conditioning.