automatic :format suffixing in helper methods?

Is there a way to automatically prefix a format in all helper methods?
like: link_to ?

So if I had an xml all links would probably be /users/1
and that is fine but what happens if I have a resource for mobiles
like /users/1.mb and want all the links in it to have a ".mb" suffixed
to it?

does anybody know if there is a patch or plugin that lets you keep
these two features?