Ok, so Sergey Brin decides to become immortal. He allocates a trivial share of Google's bazzilion dollar profit to research, hires the best minds, and starts eating more healthily, doing more exercise, and cutting down on the cocaine and ecstasy.
Let's say that given enough time, computing clusters, scores of hapless test subjects, and truckloads of hundred dollar bills to burn, these geniuses find a way to stop aging, and also cure various irritating infirmities of the body, such as cancer, heart disease and all transmissible diseases.
Brin is now free of aging and disease. His next concern is that he'll go crazy due to human minds not being design to work for that long. Out goes another bazzilion dollars, and boom, thanks to some advanced neuro-prosthetics, our lovable gazzilionaire now has a billion-year memory capacity.
All of this is still firmly within the realm of real-world physics. Now, we run into a problem. Brin now asks to be made immune to all normal weapons, as well as fire, suffocation, starvation, crushing, piercing, slashing, acid, cold or electricity. Ideally, he'd love to be able to survive anything short of a thermonuclear detonation a few meters away.
How much of this is in any sense achievable without technically breaking physical law? You can assume tremendous and compact power sources and any sort of nanotech you need. So a nanomesh that fixes wounds and restores body shape from a stored backup would be ok, but anything outright magical is out.
While so called mind transfer into a new body is all very interesting, and will obviously be Brin's plan B, he's strangely unwilling to have his primary body die in horrible agony, only for some body double with his memories to inherit all this wealth and power. He's more interested in direct technological ways to gain (near)immunity to being killed in the ways listed above.