So it sounds like Google will soon be able to pop up a warning saying I should go for a medical checkup because they've detected an increase in left-hand errors that often occurs prior to a stroke. And this is without Tango - that will yield far more data about our physical well-being.

Every advance humanity makes can be used for good or evil. On the whole, we tend to find more good than evil in most of them, and maybe global data capture will be the same.