I'm giving you an even harder task than I have. Convince someone (i.e. like me) to whom this is an obvious implementation of a trivial function, that it is not obvious or trivial.
I'll do my best, though you probably will refuse to undertake the first part of the exercise: thrust your mind back to December 22, 2005, the day before the patent application was filed, and block out everything you've seen since that date.
To unlock their phones, people do things like entering a code or holding down a physical key, because almost everyone's phone has physical keys. Others have flip phones and merely open their phone to wake it up. There are a few phones out there with resistive touch screens like the Palm line... they too use physical sleep/wake switches.
In a somewhat related field, Micron has had a patent application published for unlocking computers by moving the mouse in a geometric shape, such as a line, square, or triangle. They also talk about doing it for touch screens, like those on kiosks or point of sale terminals.
So, say you want to come up with a new, intuitive way to unlock a phone? What do you invent?
Now, I'm sure you jumped up and yelled "slide to unlock!" But is that really true, if it's really 2005 and you've never heard of that?
Plus, say you did implement a slide to unlock feature... would it be like Micron's or Neonode's: draw a geometric shape on a screen with no indication of success or failure or other response until the figure is complete? Why, that increases security, since an intruder wouldn't know that they failed as soon as they deviate from the required line! That seems like a great idea, right?
Back in 2005, no one had thought of having a dynamic image following the user's finger as they drew a line to unlock the phone. No one wrote anything about it, made a prototype, or even apparently mentioned it in passing.
Now jump forward one year, to December 2006... There are still no capacitive touch screen phones on the market. Slide keyboard phones are really popular and, of course, unlock when you physically slide out the keyboard. There are still plenty of flip phones. Palm has a great color smart phone that you unlock with a button on the top (it also doubles as the IR port). How come no one has implemented a slide-to-unlock system if it had been obvious for a full year?
Now jump forward another year. Apple's iPhone is released to great fanfare and includes a slide-to-unlock system. It's the only one on the market that does - which makes you wonder if it's really been obvious for two whole years?
Jump another 18 months. It's now fall 2008 and Samsung comes out with its first modern smartphone. And it implements slide to unlock. In fact, everyone who has put out a smart phone after the iPhone is using slide to unlock systems, including even Palm, who had smart phones before the iPhone that didn't use it. If it had been obvious for almost four years, why hadn't anyone else done it before the iPhone? Was the iPhone the inspiration for everyone? And therefore, can you really say that, years before the iPhone, it was obvious?
If an idea is relatively trivial to implement, but no one ever even had the inkling of a thought to doing it, is it obvious? Or is it one of those simple, beautiful ideas that change an industry once some inventive person first creates it?