The most obvious use of TrueVisage is as a mirror. You get your choice of the geometry of a glass mirror, or the geometry of an external observer's view, where your right ear will be on their left. But it's a mirror, and like real mirrors, it doesn't take photos, or video clips, or sing your favorite disco songs. Well actually, it will take a photo and add it to your camera roll, if there's information in the current view you'd like to refer to later.
But wait — there's more! You can use the front camera or the rear one, turn on your iPhone's flash or not, and stretch the image to see a closeup with good resolution. That flexibility allows you to use TrueVisage to read the teeny-tiny serial number on a poorly-lit piece of equipment, for instance — a job which would otherwise require a flashlight, a magnifying glass, and three hands. Save the image to the camera roll, and transcribe the identifiers later, or mail the photo to the vendor's tech support person.
This developer makes well-designed, useful tools to solve real problems gracefully. I've bought 5 of them, and find them all useful — frequently, or rarely. When I need their particular function, I'm glad that I've got them.