Ask.com has added some new features to its Ask for iPhone app, largely based on feedback it received since it was initially launched last November.

More than 500,000 people have downloaded the app, and Ask hopes the new features will attract even more users. The iPhone app basically returns the best answer from the Web in response to user questions, and if the Web’s best answer isn’t sufficient, the service leverages proprietary technology to route the question directly to a relevant Ask.com user.

One of the main new functionalities involves the ability for users to follow each other. They can pinpoint people with specific expertise or knowledge through the community Q&A. (There are settings in the app so that if you don’t want to be followed by a particular somebody, you can block that person.)

Ask does not yet offer an Android app, but that’s in the works for debut later this year. Feedback that Ask has received about the initial iPhone app also helps in the development of the Android app, according to Jason Rupp, senior director of Product Management at Ask.

Ask reports a major uptick in traffic from mobile devices to its Web page – over the last two quarters, it’s seen close to 100 percent growth in visits from mobile devices and a 50 percent spike from the iPhone alone.

“What we’re seeing is users are becoming more and more engaged on mobile devices,” Rupp says, noting improved form factors on mobile devices and better browsing experiences. It used to be that usage of apps picked up during the work days and fell off on evenings and weekends, but that trend is reversing primarily because of mobile devices.

Other general app updates available today include a retooled results page; the ability to modify a question after it’s been asked to better focus responses; spelling suggestions; increased answer speed; and log-ins with Facebook or LinkedIn.