If you slide down Notification Center, bounce it, and press the home button mid-bounce, the entire phone is disabled until it is rebooted. Pressing home in the middle of a NC bounce animation makes it pop away if it's done at the right time. After it pops away, pressing the home button once won't do anything anywhere, only double taps will work to get to the app switcher. Also, the camera won't work and Siri won't work. Someone who does this by accident obviously won't know why their phone is acting up. This is also present in 9.1 beta 5. See if you can achieve this like I did.