iOS6 included a new feature called Guided Access. Essentially what it does, is allow you to lock an iOS device into a certain application and disable touch input on certain areas of the screen as well as the home button.
This has obvious benefits for iViewer, an iOS device can now easily be set to run only iViewer and nothing else. Ensuring that it is not possible to fiddle, or to try and use the device for another function other than these for which it is intended.
Using Guided Access also disables the slide to unlock function.
There are however a two points to be wary of when using Guided Access:
For Guided Access to work with iViewer, you must ensure that the Multitasking setting in iViewer settings is turned on.
For a short video on how to configure and use Guided Access, see this video.
For more info on iOS6 and iPhone 5 see this page.