@ Pete Spicer
Isn't a caveat of patents that it should be "non-obvious"? How else would you propose to "securely" (as in non-accidental) activate a feature when your only method of input is a touch screen of some sort?
FWIW, I would call prior art. I had a little "organiser" thing with a touch screen and stylus back circa '98. It had an on-screen keyboard, I could "draw" words (like Swype) and I could tap-drag to switch the backlight on and off (this was important for running off two AAAs the backlight was horrendous on battery consumption). The tap-drag was remarkably similar to Android's unlock. The only difference is it turned a feature on and off, not unlock. Same principle. If I could find the thing, I'd power it up and drop a video on YouTube. I wonder if the Psion5 did anything similar, given it's touch screen and stylus arrangement.