> At some point you will hold the compute power and memory storage of a Cray Y-MP in your pocket.
I believe that point would be Today.
Newer smartphones have 1GiB RAM. A common SoC implementation, nVidia Tegra 250 T20, has >5 GFLOPS in its GPU and two 1GHz integer cores.
According to wikipedia, the original Y-MP series topped out at 8 processors of 333 MFLOPS each (total 2.7 GFLOPS); and a princely 512MiB of RAM. The minimum configuration had 128MiB RAM and 666 MFLOPS.
So you can certainly have the power of *a* Y-MP, and arguably as much power as the biggest configuration you could order when Y-MP was announced. Not to mention a whole cluster of Cray-1's (4MiB RAM!, 250 MFLOPS if you really push it).
Later derivative models (which tended to drift away from the "Y-MP" designation) may eventually have gotten as powerful as a throwaway desktop available today, e.g. $900 Lenovo Ideacentre 7727-5DU with 3.4GHz quad-core i7-2600K (+ 3.8GHz turbo + hypothreading), 200 GFLOPS video chip (Radeon 6450), 12GiB RAM, 1.5TiB disk.
Yes I know GPU GFLOPS are talking about single precision and they're only about 1/4 as fast at double precision. So if your desire for a Y-MP includes double precision floating point vector processing, you'll still need to drag around a wagonload of Cray hardware to (slightly) beat your smartphone.
The Cray probably blows the socks off the desktop, not to mention the phone, in I/O bandwidth. Or maybe not. It didn't have a bunch of USB & firewire ports...