[thumper]

Another example that came up while I was testing the Zeo: their tracker asks how much caffeine you have after 3pm daily. While I was messing around with their graphs, I discovered a clear correlation between cans of soda and poor sleep the next night. That might seem "obvious", but it was a real surprise to me because I had never noticed any relation at all. At the time I was trying to stop soda at 6pm and I go to bed at midnight, so it was even more surprising that the effect was so long lasting.