IndexicalDemon

The crucial information is up and down ticks of the ES-mini futures at the Chicago Mercantile Exchange. These lead the S&P500 (SPY) index funding in NYC (by 4 milliseconds), and the ES-mini ticks up and down about once per second. This few bits of information carries huge value since much of the world's equity market responds to it. See https://arxiv.org/abs/1302.5966

It's a cool system. There's a slight disadvantage that the satellite-to-ground link is at 10-15 GHz for users, so it will go down in a heavy rainstorm, and some fraction of the time due to other atmospheric effects. Should be reasonably reliable but far from fiber, and it will be interesting to see what uptime they guarantee. Assuming this all ever actually happens.