Yahoo and Google were among the first companies to let people scour the web by typing some words into a search box. Now both companies are building a new kind of search for mobile that aims to do away with the query.

Earlier this month Yahoo updated its Aviate app that lets Android owners customize their phones' home screens by adding a feature called Smart Stream. Smart Stream aims to function as someone's personal assistant, anticipating whatever information a person might need and making it available on the phone's home screen.

Like Google's personal assistant app Google Now, Smart Stream pulls information from various apps on a person's phone like their calendar and location, as well as other signals. For example, if something is plugged into the phone and the person has a conference call scheduled in one minute, Smart Stream would determine that headphones were likely plugged in for the call and automatically show the phone number to call when the person checks the Smart Stream screen on their phone.

For both Yahoo and Google, these personal assistant apps are bets on the future of search. As people start searching more often on their phones while on the go, they may be more impatient about getting to whatever information they're after. Typing out some words and scrolling through a list of links may not take that long, but technology is about making people's lives easier, including making the tasks they need to complete quicker. So as web search improved on the need to pull out a phone book or go to the library to look up information, these personal assistant apps aim to improve on the need to tell the computer what information you want to look up.

"When we think about Smart Stream, we're answering the question of what do you want to do next," said Paul Montoy-Wilson, a former Google product manager who co-founded Aviate before selling the app to Yahoo in January 2014 and now serves as product manager of Yahoo Aviate.

To answer that question, Smart Stream accesses a phone's location history, app usage patterns, calendar information and search history, Mr. Montoy-Wilson said. The app also takes into account how people use Smart Stream to recalibrate what information appears to be of most interest to an individual when using the personal assistant.

"For example, let's say we predict you want to go to a movie this weekend, so we surface the upcoming movies this weekend in a theater nearby. We can see: did you engage with that card, and then not only did you engage with it but what movie did you click on, and not only what movie did you click but did you click to view a trailer or buy a ticket. All of that data helps us to personalize that experience for you," Mr. Montoy-Wilson said.

That's not all that different from Google Now, which can do similar things, like telling someone when they need to leave to catch a flight or show up for a restaurant reservation by factoring in traffic data, as well as the individual's calendar. And Google is building on Google Now with Now on Tap, which can stretch beyond Google Now app to show relevant information while using other apps.

However, one area where Yahoo's Smart Stream can diverge from Google Now is its use of the information tied to a person's Yahoo account.

"If you're a Yahoo Mail user, we'll begin to surface interesting cards based off of your email. If you have a flight coming up, surfacing flight-related information. If you have a package arriving soon, surfacing when that package is going to arrive and allowing you to track it," Mr. Montoy-Wilson said.

How Yahoo's Smart Stream will translate into revenue remains to be seen. Neither Google Now nor Yahoo's Smart Stream feature ads, and letting brands mess with someone's personal assistant might be a dodgy proposition. However, being able to anticipate what someone wants still has value for companies like Google and Yahoo that operate large ad-tech businesses charged with aiming brands' ads at the right audience.

"Effectively, anticipatory computing is trying to understand the intent of the user before you type in a query. If you understand the intent of search, it's a huge business," Mr. Montoy-Wilson said.