What is the easiest way to redirect when on a mobile browser?

I've been searching all over google and the only thing that made relative sense was a .htacces rewrite rule. But that didn't work, it just errored out my wordpress site.

http://webdirect.no/mobile/apache-rewrite-rule-for-iphone-users/

that was the one i tried out with no luck...

either way, there has got to be an easy code to just put into my index.php file that would redirect the site to www.mysite.com/mobile/index.html

I've used this:
http://detectmobilebrowsers.mobi/

And it seems to work very good.
I think you can try it for free and test it out.