Hmm, I do have tap to wake and that is giving me an idea. You can pull down the status bar while the phone is locked and in the bottom right corner there's a power button. So theoretically my leg can double tap the screen, pull down the status bar, tap the power button and confirm. Feels like a bit of a stretch but who knows. I've never had it randomly turn off while I was using it or while sitting on my desk after all ¯\_(ツ)_/¯