afaik this has been requested before (along with an android application which i definitely remember being suggested) however it is rather low on the list of dev priorities so it may be some time before we ever see anything.
Apps for all three major mobile platforms have indeed been requested, as has Tapatalk support. On that note, improvements to the mobile format of the site/forum is also on the list. Like ssddx has said, though, don't expect it any time soon; just know that it is in the works and that we will roll it out once it's ready 😛