I’d read about this shortly after the 9/11 attack and it was really fascinating, but I couldn’t find my original link anymore. The link above is a recent article because the same device seems to have predicted the tsunami.
The short version: There are 65 “random event generators” in 41 countries that constantly generate zeroes and ones, like an electronic coin flip. The results are recorded and can be displayed on a graph. The laws of probability dictate that there should always be a roughly equal number, which shows as a flat line on the graph. Certain major events in the world (the funeral of princess Di, the 9/11 attack, the tsunami) since the first generators were set up in the 90s have caused big spikes in the graph, as the numbers stopped being as random, before the event actually happened. The full article is definitely worth a read, it’s really something.