There are literally dozens of night vision apps in the App Store, all designed to let your iPhone, iPad or iPod touch see better in the dark. The developer of the Night Vision app (US$3.99) says that he's developed some complex algorithms over the last two years to let your camera perform much better in a very dark room.
The app supports both cameras on your device, and lets you see adjustments in real time before snapping the photo. You tap to focus, and there is a digital zoom, although I view all digital zooms as next to worthless. Once your photo has been taken, you can save it out to the camera roll, email it or share via Twitter, Facebook or Dropbox.
Using the app is easy enough: You can try and shoot in color, but camera chips do a bit better in mono, so I tried that too. Mono photos have the traditional green, night vision look.The app supports HDR, and while you are framing your photo, you can slide the amplifier gain up and down.
In a very dark room, illuminated by only a faint nightlight, the image looked pretty detailed and relatively noise free. However, when I tried the same shot with the unaided iPhone 5s camera, the results were pretty similar. It seems that Apple's camera and software has really been improved since I tried low-light photos on my iPhone 4s. Still, in a really dark room, you could push the Night Vision app even further, although with a pretty big noise penalty.
I don't think Night Vision is useful for clandestine surveillance work, but certainly in some situations, it can see more than the unaided iPhone or iPad camera can see. It's just not that dramatic a difference. The same developer has a night camcorder app that we reviewed without too much enthusiasm for its marketing technique, but we found the app performed OK.
As mentioned, there are many free Night Vision-type apps in the App Store. Most get pretty low ratings because user hopes are greater than what these things can do. Night Vision, as reviewed here, seems to do a bit better than the free apps I looked at, but don't expect miracles.
Night Vision is a universal app, and requires iOS 6.1 or later. It's been optimized for the iPhone 5.