Ask Chris Dancy what he ate on Aug. 11 of last year, and he can tell you (Chick-fil-A). He can also tell you about the weather that day (83F), what music he listened to (Kelly Clarkson’s Walk Away), how many e-mails he sent (21), how long he slept (8 hours and 35 minutes), how many steps he took (8,088), and when he took his dogs to the park (1:04 p.m.). Dancy, 45, doesn’t have an amazing memory. He’s an extreme life hacker: He collects information about himself and his surroundings from 10 devices he wears or carries and 13 more in his home and car. He also catalogs virtually all of his online activity. The exhaustive record-keeping is an effort to discover the systems that shape his behavior so he can tinker with them and live better.