1) Simple redirection
If their IP address is in that array, it’ll redirect them to another site.
2) Adding a touch of remembrance
Of course, they may move their IP address and try to check your site later. It’s not common but it can happen and it’s worth being ready for it. We need to add only a little bit more code.
3) Really being devious
Of course, it’s one thing to forward them to 4chan or some other black hole of the internet, but we can be more creative than that. The first thing we can do is to forward them to http://oursite.com/index2.html, where this new link goes to an old and rubbish version of your site. Of course, all the links on this page need to be broken, etc and the page should not be indexable by Google. If you want to be downright malicious then you could add in javascript to try and lag their browser up, load in tons of big images from Wikipedia, etc.
There are many fun things you can do, but the core is that you want them to either not be able to see your site or to see a modified version of your site so that they think you have a terrible design, broken links and possibly a load time only a modem user would think was real.
