Is there an app or setting to lock an iPad in a Presentation mode, so other apps can't be accessed? Not really an iPad user so thought I would ask here.

As an organisation we want to place some presentations on iPad minis 
(much in the way that iPads are used in the Apple Stores as information sources next to other products).

We want the user to be incentivised to view the entire presentation so ideally we don't want them to be able to leave the presentation. 

Are there any applications that allow presentations to be locked?
Ideally, presentations would be built in PowerPoint or HTML/CSS.

I appreciate any input you can provide.
The Apple-sanctioned method to accomplish this is the use of the Guided Access feature in iOS6. Settings > General > Accessibility > Learning > Guided Access.