I have an iPhone 4S (iOS 7) and my Hold Button is broken. Consensus on the Internet seems to be that if this is the case, one can maximize phone capability by activating Assistive Touch (Settings > General > Accessibility > Assistive Touch > On).
I've done this. And I can now turn off my phone by holding "Lock Screen" under "Device" in the Assistive Touch menu.
But how will I turn my phone back on once it's off?
Is there any way to simply restart from Assistive Touch?