What does '眼观鼻鼻观心' represent? Obedience or an attempt to be invisible?
眼观鼻 (eyes looking at the nose) = 'look down'

鼻观心  (nose pointing at the chest) = 'lower one's head'

眼观鼻鼻观心 = 'look down and lower head'

It is a graphic description of a posture

This posture can be used to express many things, like humbleness, submissiveness, relaxation and concentration

The two most common activities that require someone to 眼观鼻鼻观心 are praying and meditation . 

'眼观鼻鼻观心地冥想' = 'look down, lower one's head and meditate' (require relaxation)

'眼观鼻鼻观心地祈福' = 'look down, lower one's head and pray for blessing' (require humbleness and concentration)