It was one thing for Gmail to ask “did you intend to attach a document to this email?” based on your use of the word “attached” in the email. But it moves things to a whole new level when an app analyzes your digital bread crumbs and tells you stuff that you haven’t even thought about. The services guess what you want to know based on the digital breadcrumbs you leave, like calendar entries, e-mails, social network activity and the places you take your phone. Many use outside services for things like coupons, news and traffic.