A CYNIC might dismiss the "quantified self" movement, whose adherents use an array of gizmos to record all aspects of their physical existence, as gimmicky navel-gazing by geeky workout nuts, eager to gamify ever bigger chunks of life. That, as Babbage has recently come to realise, is unfair. Better information about your actual exertions makes for more informed decisions. This is as true of exercise as it is of personal spending, say. Little wonder that, as monitoring devices become smaller, cheaper and better integrated with smartphones, more people are embracing their quantified selves.