The twice-weekly segment “App Wrap” reviews some mobile device apps that share information about the terror attacks of September 11, 2001. NY1’s Adam Balkin filed the following report.

It's been nine years now since September 11th became more than just an average transition day between summer and fall. Mobile device users can now remember and even learn a bit about that fateful day via some iPhone apps.

Explore 9/11

"Explore 9/11," created by the National September 11th Memorial and Museum, can be used by any user anywhere, but it is most powerful for users at the World Trade Center site. The app offers a guided tour of the area, complete with pictures and audio eyewitness accounts presented by first responders and others who were in the area that day. As users walk around, GPS can pull up a whole bunch of pictures taken from pretty much any spot within about a quarter-mile radius of the site. There is also an interactive timeline.

Those who are interested in what things will look like Downtown going forward can look at shots that compare what the area looks like now, with what the memorial will look like down the line.

"Explore 9/11" is a free app for the iPhone, iPad and iPod Touch.

9/11 Numbers

A much more basic and low-tech app is "9/11 Numbers," which simply ticks off a bunch of numbers related to all the planes and civilians attacked that day. It starts from zero -- the number of survivors from the North Tower above the point of impact -- and moves all the way up to 422,000 -- the number of New Yorkers who suffer from post-traumatic stress disorder because of the September 11th attacks.

Some of the app's numbers indicate what has happened as a result of that day, like the 22,000 bombs dropped on Afghanistan in the six-months following the attack.

"9/11 numbers" is free and also available for the iPhone, iPad and iPod Touch.