The new personal digital assistant built into Windows Phone, called Cortana, does similar tricks.

In theory, this can put the gadgets that know the most about us to work helping us live better lives. In practice, the context is there, but the predictions are not quite — yet. And the privacy trade-offs may be too much for some people to stomach.

Apps that know who and where you are can be undeniably useful, said Robert Scoble, a co-author of a book about contextual technology, “Age of Context.”

If you give an app access to your email so it has your travel itinerary, for example, it can alert you when there’s a problem with a flight, show you alternate flights and let you tap one or two times to rebook — especially if the credit card information is stored in the app. That situation played out for Mr. Scoble recently, he said, and “that night, I won at life.”

Image Credit... Minh Uong/The New York Times

A generation of mostly brand-new apps is trying to add new conveniences by scanning your signals.

EverythingMe, available only for Android, does something Apple’s iOS will not allow: It takes over the home screen and then rearranges and recategorizes your apps. This type of app is called a launcher. A similar app is Aviate, currently available on an invitation-only basis.

Of the two, EverythingMe is more powerful and it required virtually no setup before it started learning from my behavior. It categorizes apps into obvious folders, like Social, Games, News, Weather and Music. Those folders also instantly generate related content from popular websites, as does any folder I create and give an obvious name, like Kids.

That’s slick, but not contextual or predictive — it’s just a nice way to organize your phone.

What EverythingMe does well is serve up a rotating collection of four home screen apps that change according to the time of day, my location and how often I use particular apps. In the morning, I get a custom icon, My Day, which shows calendar events and apps I use often in the morning, like Twitter. I might also see Traffic, Calendar and Hangouts, which I use for chatting with co-workers.