Tests show standard UI inputs are understood the best. Just use the checkbox for your website.
Now considering how widespread the iPhone/iPod are in use, I doubt many people would have trouble putting 2 and 2 together.
Relative to other technologies, it is not.
Also, changing the platform might require interface changes that are clearer and easier on that platform. I'm not saying iphone checkboxes are bad. I love them. But they stink when they aren't on the iphone. They even stink when they are on the iphone but in a web app.
The issue here is whether something from a new platform should be used on an old platform. No, if the tools aren't standard.
Note that new browsers and browser versions render checkboxes differently, which yields incremental changes over time.
But on a meta level, doesn't this feature strike you as a bit cargo-cult?
I apologize for not having a link to the words that have come out of the mouth of every designer I've worked with.
Just because Apple does it, doesn't mean it's the best way to do things all the time.