If those don't work for you, there are a couple of 3rd-party options as well, but neither is completely free...Tapatalk
- allows your users to browse the forum using an app on their phones. Free for you, but not for your users, and the app would require them to search for your forum first. The app supports iOS (iPhone/iPad/iPod Touch), Android and Blackberry, and costs $4.SMF4Mobile
- a nice mobile theme that allows your users to browse the forum directly from their mobile browsers without having to download or install any apps. The theme is $20 and includes a year of support and updates (after that it's an additional $20 per year for continued support and updates). It supports iOS, Android, Blackberry, WebOS (Palm) and newer versions of the Symbian OS.