Is a computer wired controlled sd card or USB flash drive feasible (like the Scylla cards connected with a laptop in prison break)?
When a computer reads the flash drive it actually reads from another computer being wired connected with the flash drive.

An SD card is a computer. You should read what an card actually is: a computer that responds to commands from the host. Some of these command should make it deliver data from its internal storage.
What it actually does is fully and completely up to the SD card's programming. Again, an SD card is just a computer with a few commands that it reacts to.
So, yeah, what you describe is done, it's done to develop SD cards and card readers, it's done to test software and it can be done in arbitrary ways.