which claims it can wirelessly deliver content to Apple devices among others. However, the video which details the use of this gizmo is a little old and remarks indicate that Apple has been busy blocking the functionality of such devices.
Is there a device which allows portable streaming of content (on a USB stick, SD card, or portable HDD) onto an Apple product?
The HooToo is pretty quirky, but it should provide standard DLNA or smb shares. I've used it with Android and it works with minimal functionality, but then again, its much easier to deal with local content on Android tablets. You can try to find an APP for apple that is a DLNA media player and see if that works.
You'll probably want to look for something a bit more robust.