iOS: Technically, Apple doesn't allow game emulators into the App Store. However, every once in a while, an emulator sneaks in. Remote File Manager is one of those apps.
On the surface, Remote File Manager is simply a file browser for Dropbox and FTP. It can open a wide variety of files in the manager, and that includes SNES roms with the SMC file type. Drop a SNES rom into your Dropbox folder, launch Remote File Manager, select that SNES rom, and Remote File Manager open an emulator right in the app.
It only works with SNES games, but it works really well. Users over at Touch Arcade are reporting that it works with some external controllers, including the iCade. Remote File Manger is universal for both the iPad and the iPhone, so grab it while you can.
Remote File Manager (99¢) [iTunes App Store via Jake Smith]