My friend Frank works for Canon in Manhattan, and occasionally gives demos in a room with locked-down iPads. Sometimes those iPads need to be rebooted—but Frank has no access to the sleep/wake switch ostensibly required to power off an iPad.
In the past, I’ve suggested that Frank “reset” something (under Settings -> General -> Reset) that’s easy to set again; resetting Location & Privacy settings doesn’t mess too much up, and it restarts the iPad when you tap it.
But there’s a better way. Also in the Settings app, head to General -> Accessibility, and and turn on Assistive Touch. That adds a draggable dot control to your screen, meant for people with physical challenges that prevent them from triggering certain iOS actions the traditional way. Tap the dot, then tap Device, and finally tap and hold Lock Screen—a software equivalent of the sleep/wake button. After a few moments, the familiar Slide to Power Off message appears, and you can shut the iPad down.
Source: Mac OSX Hints