Smart Sign

Summary
Smart Sign is a special app that shows product specs and is installed on the "Smart Sign" iPads inside Apple Stores. This app can’t be exited with the home button. There is a gesture to quit apps on "Smart Sign" iPads which is shared on a need to know basis among employees. The gesture does not return you to the home screen but returns you to AppleConnect.

Technical Investigation
The app itself is not what disables the home button; it is system-wide and enforced by SpringBoard. The key SBStoreDemoAppLock in com.apple.springboard.plist enables this functionality. A disassembly of Springboard.app/Springboard reveals that there is no special gesture built in to Springboard to emulate the home button outside of multitasking gestures (if they are enabled on an iPad that was connected to Xcode). However, the app may have a gesture recognizer that performs an "exit(0)" call to quit the app.

Apple sets the key in com.apple.springboard.plist by using a mobile configuration profile installed on the device. The profile is set to prohibit removal of itself.