I took a quick peek at what Ajahn Brahmavamso has to say about breath meditation.
I am certain that my progress along sustained awareness of breath is far behind a person such as Ajahn Brahmavamso, but the one thing I can relate to in a writing of his on the net is the not "interfering" part that comes with breath-awareness.
Also becoming completely engrossed in each and every phase of the breathing process is something essential I have come to appreciate. The one pitfall I have recognized is an expectation I have that bodily calmness will come hand in hand with breath awareness. This becomes a stumbling block for me. But the minute I give up on trying to achieve bodily calmness and come back to the basic awareness of breath, the bodily calmness simply follows.
I realize the whole time that I've been trying to screw the lid off of a jar of pickles in a counter clockwise direction. Whether we choose to break it into 15 parts or 100; an essential step towards understanding the effects of the breath on the body and mind is a full commitment to the breath first.
I personally step out, in many other people's opinions, from Buddhism in my connection to my body. I realize that the body is meant to operate in a certain way. For me, the loftiness of insight comes through a fairly straight forward, albeit magical reaction within the context of letting go or initiating non-attachment to the body.
My practical efforts can be summarized like this. With the help of understanding one's breath...
The base of the spine, in the morning, releases testosterone and keeps the lower regions of the body healthy
The second lowest part of the spine, as the morning continues, encourages healthy bladder function through a release of different but similar biochemicals like testosterone
The region of the spine, right at noon, where the stomach is located encourages healthy bowel movement with a similar release of bio-chemical endorphines or steroids (I can't say what genera these "chemicals" belong to for certain).
The region of the spine, in the afternoon, right behind the heart, or the heart itself releases an especially important thing. This thing, and whatever it is, helps to reduce any adrenaline produced in the bodies metabolism of food. This thing is also quite related to metabolism.
The neck region, in the evening, releases insulin.
The base of the neck near the back of the head, promotes open and healthy nervous tissues - via yet another kind of molecule. At this stage the molecules are becoming less and less material in nature; therefore harder to explain and define.
The front of the head, as the evening continues, promotes healthy bone structure. And when this important area is concentrated on properly the effect it has on the entire bodies bone structure is, to the observer, like going completely numb. This is why, having experienced it for my self, I suspect it shares something in common with the third jhana. I have no way of proving that. It is a suspicion of mine.
The top of the head, as the night is coming to a close, promotes healthy muscles with the release of the last biochemical which can rightly be called "material".
The places which then follow now correspond not to bodily functions and the promotion of their well being, but rather speculative views and a healthy distance created from those views, or, in other terms, a spontaneous revelation of how these views exist within a person. They are, so to speak, immaterial.
While most people are asleep, around 12:30 or so...
Another region near the back of the head; another region near the front of the head; another region near the top of the head; another the region right in the center of the head; and the region right in the center of the heart open up; in the same order - to promote:
A perception of:
Consciousness extended around the objects which surround the person
Nothingness, as if it were the shadow of the hollows which form inside the emptiness of a person's rib cage
Neither perception nor non-perception; and
The heart's release from the bondage of attachments.
So as non-Buddhist as all of this sounds, it's how I understand the body and it's more Yogic than anything else except that, in my experience, the nature of these "precious-points" put the context of jhanas and immaterial jhanas into an understandable framework (for me anyhow).