Focused ultrasound is a non-invasive surgical method http://www.fusfoundation.org/MRgFUS-...asound-surgery
It's non-invasive imaging method can be MRI or even ultrasound itself.
So we have a method for precisely destroying and precisely releasing chemical in any part of the body.
(Another method is precision x-rays/gamma rays like in the cyberknife system, but let's ignore that for now)
If those chemicals can grow any part of the body too, like the "pixie dust" of Stephen Bodylak described below (extracellular matrix powder) then we also have mechanism for growing any part of the body precisely.
These robotic machines would be used everyday to selectively destroy/grow all parts of the body, and so, over time, all parts of the body become new again. Thus defeating aging and the diseases associated with it, hence immortality.
To do carry this all out, set up 100,000 robotic ultrasound machines in a warehouse, and automatically robotically (using machine learning/computer vision) run experiments en masse on mice/pigs etc. to determine the correct intensity/dosage for destroy/growing any particular parts of the body. (Use machine learning to transfer knowledge of how mice/pig dosages translate to human size/levels).
Thus, a potential immortality device in a few months.
Another thought, whole body vibrations are used to grow all parts of the body (with circulating growth factors) and the focused ultrasound is used to selectively destroy the older parts (over time, safely).
Also, ultrasound is has been demonstrated to encourage growth/repair of tissues in the body and in the lab (it's the basis of therapeutic ultrasound http://en.wikipedia.org/wiki/Therapeutic_ultrasound
). So it might to destroy/grow without even the extra growth chemicals.
What are critiques of the above. I'm looking at this from the point of view of what is possible given unlimited funds (1-100 billion dollars).