[rdtsc]

That's an interesting one. Maybe complicating instructions might take too long to encode, but making it a simple buy/sell trigger for one particular security could work? But also going over too long a distance means the stock markets are closed in that part of the world.

There is also a satellite company LeoSat that was trying to build a low latency long distance network of low flying satellites with laser links between them. Guessing that's a "tad" :-) (few billion) more expensive than a pair of shortwave transceivers. But if money is not an issue they say they can do 1.5x faster than terrestrial speed:

http://leosat.com/media/1115/leosat-finance.pdf

100ms NY to Tokyo, for example. Not bad.