If your subject doesn't move, two cameras can be approximated by taking two pictures a set distance apart.[1]

Also note that the method used by this app is very short ranged, and uses the LCD's backlight while it's imaging, so there's zero feedback, making any kind of interactive application impossible.

1: There are third party accessories to make this easy and repeatable, built with varying levels of quality. Here's a fairly cheap one, circa 2003: http://www.dansdata.com/photo3d.htm