OnChrome is a Firefox extension that opens only the urls you want on Chrome.
Specify once what you want to open with Chrome. The extension takes care of the rest... whenever you visit one of the target urls on Firefox (because you entered the url or because you followed a link) that Firefox tab is closed and the same url is opened on Chrome.
Why is this useful? because you may want to use Firefox but need to use sites that only work on Chrome.
Because Firefox can't talk directly with Chrome, the extension requires you to install a native application that does it. You open the menu app, press `1` if you want to register it (or `2` if you want to unregister it) and that's it.
Visit the Native Applications page to download them.